THE SCENT OF SEX — but not for you

  • Diarmuid Breatnach

You sniff the scent of blooms in the air and it pleases you. But that’s not what it’s for – the scent was not manufactured to please you. Scents derived from plants are used by humans to add to their sexual allure and plants also have a sexual function in producing them — but it is not humans the plants are trying to attract.

The scents are there to attract pollinators, insects, mammals or birds that will go to them to collect pollen and/ or nectar, in the course of which they will spread pollen from plant to plant and bring about fertilisation.

There are huge numbers of different chemicals producing scents and combinations of scents and, as the plants have developed them, their pollinators have also developed the ability to distinguish between them and to home in on the appropriate ones. It is likely that inside the pollinators some kind of receptor is created which is keyed into the specific scent, in much the same way as sexual pheromones are keyed into receptors inside so many species, including humans.

Irish Hawthorn (Sceach Gheal) bush or shrub in bloom. Its blooms produce a scent more pleasant to humans at a distance than very close up.  (Source photo: AP.Pfeiffer)

Irish Gorse (or Furze) (Aiteann) in bloom. The scent often reminds humans of coconut.
(Source: Environmental Protection Agency)

These pollinators then, quite unintentionally, dive into another bloom somewhere and like some kind of romantic couriers, deliver the pollen to the eager recipient. But unromantic really, to receive fertilisation from an unknown lover, unseen and barely felt. Yet it works, as around 400,000 flowering plants testify (though not all flowers use scent — colour and form suffice for some). And it will continue to work, as long as there are pollinators around (which is turning out to be a problem with large-scale deaths of bees, by far the most active of pollinators). But the animal kingdom? With some exceptions, its members need the presence of both sexual actors or more and stimuli to engage in sexual activity that will lead to procreation: temperature, light, foods, natural odours, shape, touch, erotic imagining, poetry, music, clothing, colour …. and yes, applied plant and artificial fragrances.

Irish Honeysuckle (Féithleann) in bloom; a climbing plant, its flowers produce a scent pleasing to most humans. (Photo source: Internet)

The scent of flowers is composed of a variety of VOCs (volatile organic compounds), most plant scents being composed of many compounds and some of up to several hundred. Collecting, isolating and analysing these compounds present great challenges to scientists but even small insects know what they mean, like an olfactory equivalent of a neon sign: NECTAR AND POLLEN HERE!.

Some plants emit scent throughout daylight and some at specific times of day only. And some not until after the sun has set. At night of course the plants do not have much competition but which pollinators will be active at night? Moths are the big group here but there are others, such as some bats.

There’s a night-scented shrub near my home that made me want to look into this subject and write about it a little. This time of year at night it is producing a strong sweet scent (with, to my nose, just a touch of urine smell in there too). You won’t find moths flying around at this time of year in Ireland and it’s not attracting bats so I guessed that it’s a foreigner and, where it comes from, that this time of year would be perfect. The shrub in question is the “Sweet Box” (Sarcoccoca confusa) and I was not surprised to find that its “native heath” is in eastern and southeastern Asia and the Himalayas.

The Sweet Box ( Sarcoccoca confusa), non-native, emits its scent at night (Photo: D.Breatnach)

People like the scent but it’s kind of sad when one thinks more about it, what it’s trying to do, like posting a message of sexual availability and procreation-wish on to a dating page and …. no-one replies.

Blooms and other parts of plants also produce scents which do not appear to have any role in attracting pollinators and scientists believe that these are defensive scents to ward off herbivores. In this case the olfactory sign is saying: “HORRIBLE TASTE! REMEMBER?” Not only that but plants can increase the production of such scents as parts of them are being eaten, to the extent that their attacker feels obliged to desist1. And some scientists also speculate that scents for pollinators developed first as scents to discourage herbivores.

Hemlock (Moing Mhear), a very poisonous native plant that looks like cow parsley. It has an aroma unpleasant to humans and probably to herbivores.

Given that some animal appropriators of plant products have learned to home in on the repellent scents of some plants this seems quite likely. Imagine a plant exuding a smell to ward off a herbivore and imagine an insect learning that where that particular smell is to be found, so is food such as nectar or pollen. The sign now says: HORRIBLE-TASTING TO HERBIVORES AND PARASITES but is accompanied by another sign that declares: FREE DELICIOUS FOOD FOR OTHERS! And the plants that most reach and “please” the accidental pollinators will naturally be more successful, be visited more often and spread their genes wider. Unless yet other animals learn to follow that scent in order to consume the plant, or lay their eggs on it for the larvae to feed on the plant. Cabbages and carrots for example, both of which have an odour we can identify, have eggs laid on them respectively by the cabbage butterfly and the carrot fly, which are then fed upon by the larvae as they hatch. And the butterfly and carrot fly find the plants by smell.

It is a difficult balance, to attract pollinators and yet repel herbivores and parasites and no doubt the balance is constantly being adjusted through the evolutionary processes of plants, herbivores, pollinators and parasites, in a kind of dance of love and death.

Cut red roses, often purchased from a florist — but do they have a scent?
(Source photo: Internet)

Those volatile compounds to be found in the scents of flowers almost certainly also make them difficult to keep fresh. The cut flowers business is a billion-euro one and growers have now produced blooms that last longer after cutting than they used to – sometimes for weeks. But scent?One of the most delightful scents to the human nose is that of the rose, about which songs have been sung and poems composed. Go into a florist, go to a bunch of roses and try and smell them — the chances are you won’t be able to.

The real thing, form, colour and scent — a pink rose.
(Source photo: Internet)

Shakespeare’s Juliet, who said that “a rose by any other name would smell as sweet”2 might say today that “A rose without a scent is but half a rose”. When you do find a rose or another flower that is sweetly scented, breathe deep and enjoy the scent … but remember it’s not made for you. It’s for another flower, through the agency of a courier, a messenger.

It’s all about sex. And it’s a jungle out there.


Sources and further information:

Flower fragrance:

Night-scented shrub near me:

Cut flower industry:



1Some plants can do this with poisons too

2Romeo and Juliet by William Shakespeare



Diarmuid Breatnach

They are all around us; they live but they are not animals. Nor are they micro-organisms – we see them clearly all in many places. They can grow on organic and none-organic surfaces. We might think they are plants – algae, moss or fungus but they are none of those — they are lichens. There are about 20,000 known species1 and they cover an estimated 6% of the Earth’s surface, able to exist in environments as different as beneath Artic snow, on salt spray-showered seashores and windswept mountain rocks and in tropical rainforest. An estimated 6% of the Earth’s land surface is covered by lichen species.2 Some are long-lived and include the longest-living things on Earth. There are species that require nothing to cling to while others can live inside rock, in the spaces between grains.3 In Ireland, 1,134 separate species of lichen have been recognised, according to the National Biodiversity Data Centre – i.e over 5% of Earth’s estimated total species right here on this little island.4

When we look at some growing on tree bark or rock, we are tempted to think of them as fungus, algae or even moss. Mosses are ancient enough life-forms and are plants, which algae are too and almost certainly much older. Fungi used to be considered plants but are so no longer and in their structure and digestion and also genes, are more akin and more closely related to animals. This will not be good news to vegetarians or vegans but the evidence is difficult to deny.5 Indeed there are some feoilséantóirí (word in Irish for a vegetarian and more apt in the context of this sentence) who already dislike eating many fungi because the texture reminds them of meat.

But lichens are neither fungi nor plants.

White and Map Lichen on rock, Old Kenmare: Killarney Rd Kerry. (Photo source: WikiIreland)


Lobaria Pulmonoria lichen, a leafy type, Killarney National Park (photo sourced from Internet)

So if lichens are not plant or fungus, what are they? Another kind of life-form? Well yes … and no. They are a combination of both, fungus and plant. At some point in the evolution of life on earth, logically after plants and after fungi had evolved, somehow some species of fungi combined with some species of alga and/or cyanobacteria6 and produced a symbiont or biont: lichen. Scientists maintain that the 20,000 estimated species did not evolve from one common ancestor but that different species appeared separately at different times during the history of the Earth.

Teloschistes chrysophthalmus on branches (image sourced from Internet)
Another map algae (Geographicus) on rock, a species that in a test has survived exposure to space vacuum and radiation, apparently unharmed. (Image sourced Internet)

Plants draw their nutrients from sun and elements in the soil (or in some cases, in the water). Fungi, like animals, cannot get their nutrients straight from sun or soil and need to break down their alimentation materials, whether flesh or plant, in order to feed on them. In doing so, fungi are important decomposing agents – in fact, the principal ones.

Vascular plants need roots not just to cling to soil but even more importantly, to draw up water and nutrients but algae don’t; when they have any kind of roots, it is to cling to a surface and that is exactly what the lichen needs too. Fungi extend and feed through root-like growths usually under the surface of what they are feeding upon, extending from the tips; they are not roots, however and break off easily. What we see of fungi is usually the spore-bearing parts above the surface, often much the smaller part of the organism.

Plants seem to grow above ground also by elongating their tips but in fact are extending from further back, adding cells to cells to lengthen the body. All plants need a constant supply of water (cacti and succulents store water but still need to draw on the supply to live). Fungi need damp conditions. But when combined into lichens, the new species can live without water for a considerable time. So, a marriage, as they say, “made in Heaven” … or perhaps in a Hell, an environment of very dry and hot conditions alternating with the very wet and cold , where the newly-wedded ancient algae and fungi set out to build their homes.

Some lichens contain not only algae combined with a fungus but also a cyanobacterium; this partner is capable of fixing nitrogen extracted from the air and is a valuable addition to the menage-a-trois.

It has been remarked by some that the marriage of plant and fungus is not an equal one, is not true symbiosis, since the fungal partner or symbiote benefits more than does the algal. The algal symbiote produces sugar through photosynthesis and the fungus only chitin, or hard structure, it is argued. However, if both partners (or three) are content with the arrangement, is that not a happy marriage? More seriously, the fungal partner may contribute other factors to the symbiosis of which scientists are only just becoming aware – for example, chemicals to repel organisms attempting to graze on them and protection from the sun.

And scientists do not treat them equally either, since the species of lichen is always determined and named by them according to the species of fungus, not of the alga or bacterium.


Xantheria parietina (image sourced on Internet)

So, if the claim is that we see them all around us, where are they? They may be seen on slate roof-tops, in patches of roughly circular white (not to be confused with pigeon or seagull excrement, which may also be in evidence). Yellow or orange patches are typically seen on stone, as is a black or dark brown one by the seaside. A bright yellow-green one may be seen on fallen twigs or on tree-bark, as may also a tufted-form green one growing on rock or tree.

Alga and lichen on plane tree during rain, Drumcondra, Dublin. (Photo: D.Breatnach)

The colours tend to be particularly vivid during or soon after rain when the cortex becomes translucent and, if there were no other reason to be grateful for the precipitation levels usual in Ireland, that would be reason enough, perhaps, should we take the time to admire the little things of beauty. Of course there are other reasons and as a Basque once said to me about the green of his native country and could perhaps even more accurately said about colour associated with the “Emerald Isle” — “It’s not green because we paint it.”

Some of the bright colours in lichens, produced by the fungus, are thought to be of use in protection from the rays of the sun and become more vivid after rain due to rapid absorption of water by the chlorophyl-holding part of the symbiont (or biont).


Lichina pygmaea – a black marine littoral species, this one photographed near the high-water mark. (Image sourced on Internet)

Lichens are considered “pioneer organisms” by botanists and geologists, i.e organisms that set out to colonise new territories. These maybe new territories in the sense that a geological change has exposed them to air, e.g from the seabed or from under ice, or from inside the earth by volcanic action or by tectonic plate collision.

Pioneer organisms need to be tough and adaptable and they often create footholds for other species, not quite so tough or adaptable, to follow after. However, given that logic dictates that algae and fungi existed before some of them combined to form lichens, the latter could not have been among the earliest colonisers of the Earth’s crust. On Earth then, they are later pioneers of newly-created inhospitable terrain.

May they be used to help create habitable environments elsewhere? It’s perhaps worth quoting these two paragraphs from Wikipedia in their entirety:

In tests, lichen survived and showed remarkable results on the adaptation capacity of photosynthetic activity with the simulation time of 34 days under Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR).

The European Space Agency has discovered that lichens can survive unprotected in space. In an experiment led by Leopoldo Sancho from the Complutense University of Madrid, two species of lichen — Rhizocarpon geographicum7 and Xanthoria elegans — were sealed in a capsule and launched on a Russian Soyuz rocket 31 May 2005. Once in orbit, the capsules were opened and the lichens were directly exposed to the vacuum of space with its widely fluctuating temperatures and cosmic radiation. After 15 days, the lichens were brought back to earth and were found to be in full health with no discernible damage from their time in orbit.

Hieroglyphics lichen (Graphis scripta) on rock, Castle Coole, Enniskillen, County Fermanagh, Northern Ireland, October
Cladonia coccifera and Cladonia diversa or Pyxidata on branch in Ireland (also known as Pixy Cup and Devi’s Matchstick but “Pixy” sounds unlikely for a name in Ireland, more likely from Cornwall or elsewhere in south-west Britain).

In some areas, soil lichens help to bind the sand-crust or soil-crust together but lichens have also been shown to chemically attack stone, thereby helping to create soil. Lichens can also help create little environments where soil may be retained and seeds of plants germinate. However, like all species, lichens are out to help themselves and some produce chemicals to restrict the march of mosses (another pioneer species but more water-reliant), with which lichens would have to compete in many areas).

When growing on tree bark, lichens do not parasitise on the tree nor harm it in any way, merely using it as a secure base. Older trees are often covered with lichen and dead trees or branches more so, associating in some people’s minds the ill-health in a tree with the growth of lichen upon it. Circumstantial evidence may suggest the guilt of the lichen but it is completely a case of coincidence: lichen is slow-growing and the older the tree, the more time lichen has had to grow and extend upon it; the tree dies because it grows old.

Green Beard lichen, Usnea species, Cornwall (photographer: Jonathan Billingsworth). Usnea is very vulnerable to polution, particularly sulphur dioxide and will only grow like this when well away from such pollutants.
Lichen-covered apple tree (sourced: Irish Image Collection)

The lichen will survive the dead tree for a period but it is not the killer. Now come decomposers: insects, snails, slugs and especially, distant relatives of the lichens: fungi. Without concern for their relatives, the fungi, along with the other decomposers, will reduce the tree to soil ingredients and thereby deprive the lichens of their base but, in time, providing more soil for more trees to grow and for new generation of lichens to attach themselves to the bark.

The fungus is not too discriminating and a particular species may combine with different algae species; the resultant lichens may appear to be different species but (since 2014) will be classified as the same lichen species, i.e containing the same species of fungus.8

The alga can also exist independently in nature but the fungi cannot. Two species in two genera of green algae are found in over 35% of all lichens, but can only rarely be found living on their own outside of a lichen.9

A green frond-lichen, Evernia prunastri
(Image sourced at Internet)

Sex and Reproduction

It is only the fungal part of the symbiote that reproduces sexually. When doing so, it produces spores (as do ferns and mosses) which must find a compatible alga in order to produce a new lichen, a symbiote of the fungus of the parent fungus and a new alga.

Some lichens reproduce or extend asexually, advancing across a surface and merging with another of the same species.

Uses of lichens:

When we discuss “the use” of some thing we generally mean its use for humans; lichens no doubt have many uses for other organisms, whether as food for reindeer during non-growing seasons or as micro-environments for tiny creatures. But for humans, the uses are mostly in the areas of

  • dyes

  • drugs

  • environmental indicators

  • geological age indicators

Dyes and Pigments:

Dyes were made from the orange Xanthoria Parietina and the grey-green branched Parmelia Saxitillis to dye wools used in traditional tweed (Harris) weaving in the Scottish Highlands10 and I myself have had the second of the two pointed out to me by an Aran Islander woman as the source for the rarely-used green wool knitted into a geansaí (pullover or jumper). Material for other natural dyes exist for example in Ireland but the issues are how easily they are obtained, how true they dye and how long they remain the desired colour and shade.

“There are reports dating almost 2000 years old of lichens being used to make purple and red dyes. Of great historical and commercial significance are lichens belonging to the family Roccellaceae, commonly called “orchella weed” or “orchil”. Orcein and other lichen dyes have largely been replaced by synthetic versions.”11

We know that red and purple dyes were much sought after and in some medieval civilisations the wearing of those colours was restricted to certain social classes and even to one individual (e.g the purple for the Emperor). Once Europeans had gained familiarity with indigenous civilisations of Central and South America, the red dye obtained from the parasitic cochineal insect Dactylopius coccus became an important export product to Europe until the late 19th Century, when synthetic pigments and dyes were invented. Despite this development, traditional hand-made textile producers, for example in regions of Mexico, continued to use cochineal dyeing. However, health concerns associated with some or all of those synthetic colourings in food have once again created a demand for cochineal and cultivation of the insect is once again economically viable, with Peru being currently the main exporter.12

Drugs and Medicine:

There is reason to believe that metabolites produced by lichens may have antibiotic effects and usnic acid, the most commonly-studied metabolite produced by lichens, is being investigated as a possible bactericide, in particular against Staphylococcus and E.coli.13

Lichens were also used in European traditional medicine, in particular based on the theory that plants that resembled human organs would be efficacious in treatment of illness of those organs. Some American Indigenous people also used them in traditional medicine treatment.

Lichens as Indicators of Geological Age and of Pollution Levels:

The science of lichenometry is a relatively new one in which measuring the type and size of lichen is used to indicate the age of exposed rock. It takes the known slow growth-rate of different lichens to arrive at an estimate of how long the rock in question has been exposed. This can be used on rock formations, landslides, stone buildings and statuary.

The tolerance (or lack of tolerance) of different species of lichen to certain types of air and rain pollutant can be used as bio-indicators. In general the “frond” or “bushy” types are less resistant to some air pollutants and the flat or “crusty” types more so. Lichens take their water from the surfaces to which they are attached and from the air and are therefore quickly affected by the water quality in rain and air.

In Conclusion:

Readers may find it worthwhile to take some time to examine the lichens growing around us, to think about their unusual ‘domestic arrangements’ and their pioneering habits. Or to inventory them as indicators of the level and content of pollution in a specific area.

And in particular, to put on rainproof or resistant clothing and to view lichens during rainfall or at least very soon afterwards.




Fungi closer to animals than plants (very short articles):

About Algae and Cyanobacteria:

About Cochineal and Social Rank by colour: (last paragraph in this section)

About Drugs from Lichens:

About Lichens as Environmental and Geological Age Indicators:

See the Wikipedia article on lichens, also



1See Wikepedia link to article on Lichens.

2Ibid (as above).


4See link to Biodiversity Data Centre website.

5See Science ABC link for example.

6A primitive plant form that used to be called blue-green algae; they are believed to have been their first mass oxygenator of the planet Earth.

7This species, also known as “the map lichen” is common enough on rocks in upland areas of Ireland and Britain (see articles on Lichens).

8See Wikipedia article on Lichens (link below).




12See Wikipedia link on Cochineal

13See Wikipedia link on Lichens, Medicinal use and the Wiki link on Usnic acid.


Diarmuid Breatnach


I knew there was a parallel universe long before I heard about the theory.

No, I don’t mean the parallel universe where lots of people live, particularly middle-class, where justice and democracy and the rule of an objective and impartial law governs. In that universe, oppressive powers who have plundered the earth and committed so many crimes to enrich themselves will meekly give all that up once you show them how many people disapprove of what they’re doing. They won’t repress you instead, with baton, plastic bullet and gas, jail, guns, helicopters, drones …. Sometimes, in my more idle moments, I wish I lived in that same universe instead of this one.

But it’s not the one I mean here.  The parallel universe I mean is another one where there is oxygen and what is necessary for carbon-based life forms to breathe and live — but it is not this one. And I didn’t find out about it through carrying out complicated mathematical computations – me, maths? Are you joking? All the same, I did use a scientific method: observation. And I have to thank flies for the discovery.

Have you ever tried to catch a fly, or to swat it with your hand? There’s the fly, lazily buzzing, wheeling around in the air. You prepare yourself. Fast, so fast, you grab and you know you got it, open your hand– and it’s empty!

Where did the fly go? Into a parallel universe. It’ll come back soon, when the danger is past for the moment. Conditions must not be that great in that parallel universe (unlike the one where those liberal middle-class people live) so the flies never stay there long. Maybe there’s a giant frog or toad there, its tongue flicking out right and left, catching flies that stay there too long.

OK, a different scenario. You see a fly on the table and move your hand evvverrrr so-o-o-o slowwwllly towards it. You must get close enough so it doesn’t have time to avoid your swat.

The fly does that strange thing, kind of like stiffening, apparently getting ready to jump and fly. It has seen you, you think. But you don’t give up. You slow down, almost stop. Maybe it will forget or won’t think your hand is dangerous.

The fly is now cleaning its face with its front legs.

“Good,” you think, “It’s not alarmed any more.” It doesn’t occur to you that the fly was not cleaning its face before and is only doing so now. You don’t suspect that the fly is thinking: “Oho! Fancy your chances? Come on then Big Thing. See, I’m just relaxed here, cleaning my face.”

Swat! Your hand has streaked out. The plate rattled and the mug jumped, spilling some coffee on the table-top. But nothing flew out from under your hand. You got him for sure!

You remove your hand and …. no dead fly! No bloody smear. Incredible! How did it do that? In that instant before your hand, ever so fast, came down to crush it, the fly simply shifted to another universe. It will be back soon, circling nonchalantly and may even return to the table, walking innocently on it and waiting for you to try again.

And not only is there a parallel universe but parallel universes! And I have reached this conclusion too, without even a pass in mathematics in the Irish State’s former Intermediate Examination (abandoned in 1991) or much study of physics. Again, achieved through observation. Sometimes, particularly when I am tired, I have observed a rapid movement of some small object across my line of vision. It is there for a moment only, originating ‘out of nowhere’ and disappearing again a few feet away. I propose that this is a fly, originating in another universe, flying across this one and, presumably, heading for yet another. No doubt fleeing from a swatting hand or other pursuer in another universe. Sometimes I can even hear what sounds like it might be fly laughter.

Why observable mostly when the eye is tired? Because the brain at this time is less receptive to the normal distractions and so therefore is the eye, making observation of other less normal phenomena more likely. Of course, this theory has not been proven, despite my efforts to catch this fly. It has not proved possible to predict the day or time when this “fly-through” might occur and also, being often tired at the time, my reactions tend to be slow. But one day ….

Of course, theoretical science has now caught up with my observations and a number of reputable scientists have been discussing related theories for decades (though also dismissed by other reputable scientists). Those supporting the theoretical concept even speak of a “multiverse”, i.e of a universe consisting of many – and some propose infinite — variables of the universe currently observable to us. Interestingly to a Dubliner such as myself, the term “multiverse” was first recorded in scientific discourse in a 1953 Trinity College Dublin lecture by Erwin Shrodinger (1887-1961), an Austrian Nobel Prize-winner in physics (and achiever of an even greater distinction, managing to live successfully with not one but two unslaved members of the opposite gender).  According to Wikipedia ‘he said that, when his Nobel prize-winning equations seemed to describe several different histories, these were “not alternatives, but all really happen simultaneously”. That is the earliest known reference to the multiverse.’

In one of those parallel universes there might be a version or iteration of myself who did not fuck up so many times, who is more disciplined and productive in the use of his free time and ….. well, that’s enough to think about. This other iteration might even like heavy metal music, be good at maths, like eating flatfish and not get into trouble with authorities.

The arguments in favour and against the existence of a multiverse have been equally convincing or unconvincing logically.

Against: We live in the universe that we do because that one provides the conditions for the existence of life. If it didn’t, we wouldn’t be here. Therefore it is the only universe capable of sustaining life and the only one in existence.

For: There is no logical reason why other universes capable of giving rise to life and therefore populated, could not exist, but with some different conditions to ours. All possible permutations. Or indeed that some would not consist of completely different life-forms, not even carbon-based. Life keeps turning up in situations previously thought impossible even here on Earth and we have long known about anaerobic bacteria.

Against: Such speculation is fruitless. We have not observed any effect or trace of these other universes.

For: However, there are some factors in quantum theory which do not explain what we can observe of this universe. And lack of proof does not rule out the possibility of the existence of something.

Against: That is true so far about quantum theory. But unless it can be proven or disproven, it is not worthy of scientific theory. We might as well fund investigation into the existence of God.

For: Aha, funding! That’s why you don’t want it studied – it might reduce the funding available for your work.

Against: How dare you!

And so on and on. And on.

And now, if you‘ll excuse me ….. There’s a fly nearby on the table …..