'The Great Schwendener Controversy '

«THE

GREAT

SCHWENDENER JANET C . N .

CONTROVERSY"

WILLIS

IT may interest others besides myself if I compile from footnotes in Standard works of the past, still in use, the Störy of the fight for the theory of symbiosis in lichens.

Every schoolboy, at least everyone who studies biology, knows the word symbiosis and some have seen the evidence of it for themselves under the microscope.

From about 1895 on this was generally accepted as the explanation of certain curious structures in the liehen body and after the turn of the Century it began to appear in the textbooks.

I had heard of Schwendener before a pencil note by my father in Julius Sachs' Text Book of Botany(1875),translated and annotated

by Bennett and Thistleton-Dyer, drew my attention to De Bary.

Sachs quoted Schwendener as having discovered by 1860 that a liehen consists in an intimate association of a fungus and an alga and explained it as a singular case of parasitism. Although De Bary had by 1865 put forward symbiosis as the true explanation, these English translators had not accepted it by 1875 though they give De Bary credit for discoveries that were to lead up to this Solution of the problem.

In the latter part of the 18th Century lichens were classed as fungi but rather peculiar ones and the early low-power microscopes were used to study them.

T h e early 19th Century brought in the high-powered microscope (400 to 600 and even 800 magnification). These were brought to bear on the internal strueture of lichens. They found the Green and the Blue-green cells among the hyphae of the fungus and took them to be spore-bodies and called them gonidia but were puzzled about where the Chlorophyll came from. They recognized a gonidial layer, still so called, above the medulla of the thallus and accounted for the chains of Blue-green cells asproduced by cell division, although it seemed most stränge that a spore should reproduce itself— something quite different from cell division as a spore grows.

Tulasne (a Frenchman) believed he had twice detected the formation of gonidia, i.e., spores, on the tips of the fungal hyphae.

That was in 1852. It was in 1860 that Schwendener (a Swede) maintained that lichens were true fungi but were distinguished by a singular parasitism. Their hosts being algae. Bornet (French) supported this.

380 Transactions of the Suffolk Naturalists', Vol. 12, Part 5 " The Schwendenerian Theory " was denounced by lichenologists throughout Europe, including two Russians. In England, Bentham, Thwaites and Berkeley and Leighton, the greatest authority on British Lichens, rejected the idea ; even Sachs, the great Austrian botanist still in 1875 would go no further than Schwendener's parasitism. Dr. Lindsay, whose book I have referred to, tacitly rejected it in 1856 and clung to the old gonidial idea (spores).

The contemporary controversy over Darwin's Origin of Species (1859) was conducted with far more heat and venom and had far more publicity than this academic quarrel. People could hardly be expected to worry about the Origin of Lichens while the Origin of Man was in question.

Then Reinke (a German) pointed out that each member, alga and fungus, was the consort of the other. This was further elaborated by De Bary (French) who in 1867, brought forward a similar theory of symbiosis. So to De Bary goes the credit for the final Solution of the problem.

But symbiosis did not reach the text books until about 1895.

By that time I was old enough for my father to introduce me to it ; he in his undergraduate days at Cambridge having followed both controversies with keen interest.

In 1895, Prof. F. W. Oliver, B.Sc., translated and edited The Natural History of Plants by Anton Kerner of Vienna. I think " Kerner and Oliver " still gives the best account of this matter.

I use Leighton (1879) at times for description of a species to Supplement A. L. Smith's Monograph—one needs his 23 page Glossary to read his English, e.g., a Ramalina is 'flaccid, subopake, reticulato-rugose or reticulato-serobiculate ; apothecia pallido— testacea vel pallido-glaucescentia ; receptaculum subtus rugosum.

Cetraria is spadiceous, fistulöse—caespitoso-fruticulose, nigro— spinulose.

Even Crombie the author of Vol. I of the British Museum's huge Monograph of British Lichens makes no mention of algae in 1894. It was left to Miss Annie Lorraine Smith to do Vol. II (1911) and introduce symbiosis in her introduction. She afterwards revised Crombie's Vol. I (1918). Her slim Handbook of British Lichens, 1921, is a necessary companion to this new Observer's Book for those who want a complete list of all species concisely described.

And now all the young scientists can talk confidently about symbiosis. But do go out and look for lichens in SufFolk. The

381 late Arthur Mayfield had recorded nearly 300 for Suffolk by 1930 and others have since found more and no doubt there are more to be found.

P.S. Since the above went to the Printers, I have heard from Miss M. M. Whiting, F.L.S., of a " Communication " this month (October) to the Linnaean Society on " some recent studies in the biology of lichens which have added to our knowledge of the nature of the symbiosis."

I must not leave the impression that when the 19th Century controversy closed with acceptance by nearly all lichenologists of De Bary's theory of symbiosis all was known and inquiry into the nature of the association of fungus and alga at an end.

Twentieth Century investigators, especialy in the last two decades, have set themselves the task offindingout by modern techniques and controlled laboratory experiments just what each symbiont contributes tÄ the alliance and how intimate their connection is.

Dr. D. C. Smith (Department of Agriculture, University of Oxford) has now sent me his " Biology of Liehen Thalli" (1962) and his " Experimental Studies of Liehen Physiology " (1963).

Thefirstsets out the problems that have recently been solved and others remaining to be solved regarding the exaet nature of the alliance and the probable evolution of the liehen. In recounting these experiments he quotes no less than 87 workers in this field in the last twenty years—British, German, Scandinavian, French, American, Canadian and at least one Russian, and not least, I think his own contributions.

So the long history of the discovery of the true nature of lichens is still unfinished.

SCHWENDENER CONTROVERSY