2G4 THE JOUENAL OF I30TA>Y 



Even in the case of the so-called podetia and scyphns-ciips of other 

 species (C pyxidata) no advance is made by regarding these as })art 

 of a special fructification ; since one does not get away from the fact 

 that any axis, in which even ascogenous hypha? may ramify, is still a 

 part of the gametophyte mycelium ; and, as in the case of a long- 

 stalked Pezizd-Q.n'^, the radial or centric organization of a massive 

 axis is the point that requires explanation. 



Without going into other complex somatic forms of Lichen, such 

 as the Immched perforated framework of Cladonia refipora or the 

 beautiful series of whorls of the radially-organized C. verficiUaia^ it 

 begins to emerge that the liclien-soma is extremely variable ; the 

 symbiotic factors are b}'^ no means conformable ; no factor of sym- 

 biosis, for example, can explain why an JJsnea should be radial and 

 PeJfi(/era dorsiventral, why Cladonia is tubular and Vsnea solid ; 

 yet if these are evolutions de novo, there must be some sub-aerial 

 cause for this divergence since the initiation of the first synthesis, 

 however much these somatic factors may be now inherited. It is for 

 the lichenologist to trace the meaning of every factor. Scientific 

 botany consists in the anah'sis of the plant-organism, step by ste]i, 

 referring each factor to its physiological origin and function in the 

 economy of the organism. Wholly gratuitous hypotheses of mere 

 adaptation to light-supply, for example, in the dorsiventral Pelti(j('ra 

 will not explain the centric habit of Cladonia, growing similarly on 

 the ground among grass, and both dry up equally on desiccation to 

 recover flexibility on wetting. The analogy of ' stem' and ' leaf ' of 

 higher land-tlora, as if lichens were physiologically ' imitating ' the 

 morphology of higher autotrophic vegetation, is of course the solu- 

 tion of the problem commonly and ingenuously ]mt forward (Sachs, 

 loc. cit.) ; but the significance of the evolution of even the factors of 

 'stem' and 'leaf in the land-plant is not completely ex])lained, 

 except as facts of observation, crystallized in academic mor})hology, 

 until it is no longer clear which comes first ^ — and such factors are 

 often expected to come ' by nature.' But things in biology do not 

 'come bv nature ' ; it is ihe object of the science to find out what 

 exactly is meant by 'nature,' as also by 'coming.' That the appearance 

 of such factors presents little difficulty to the imagination of those 

 who liave followed the progression, similarly wholly de novo, of the 

 land-])lant from an antithetic, interpolated sporophyte — as a s])indle- 

 shaped embryo, throwing out enations to be sterilized in terms of 

 leaves and sporophylls ~ — may be freely admitted; and such minor 

 points as the distinction between a dorsiventral crustaceous thiillus 

 and a radially symmetrical multibranched axis, may appear merely 

 trivial. Hut all these factors have to be accounted for. The study 

 of lichen-mor])hology does not account for them, but again accepts 

 them as facts of observation, lleally they shovild be the most criti- 

 cally explored features of the Avhole subject — if, as asserted, they 

 arise de novo in a dual symbiout, in direct response to the same 

 environment of light-supply, water-supply, gas-supph% and food-salt 

 sujjply. Why, for example, should the JParmelia and JJsnea con- 



J Bower, Ovujin of Land Flora, p. 251 (1908), 'Stem and Leaf.' 

 - Op. cit. p. 142. 



