Presidential Address. F. T. Brooks. 17 



chlorophyll. Where saprophytic or parasitic forms occur amongst 

 green plants, their numbers are limited and diversity restricted, 

 as if the loss of pigment and holophytic mode of nutrition had 

 checked their evolutionary impetus. Thus the families of para- 

 sitic flowering plants, Orobanchaceae and Rafflesiaceae contain 

 comparatively few genera and species, as if their undoubted 

 degeneracy had brought the inevitable penalty in its train. 

 Likewise the parasitic algae are few in number of species and 

 infrequent in occurrence, pointing to the same truth that loss 

 of a fundamental character leads inevitably to grave handicap 

 in the struggle for existence. The fungi, on the other hand, rival 

 the flowering plants themselves in number of species and 

 diversity of form, and it is altogether against the laws of pro- 

 bability that they have been derived from such groups as the 

 Green and Red Algae by the loss of pigment and development 

 of a saprophytic or parasitic mode of nutrition. Thanks to the 

 researches of Kidston and Lang* we now know that the fungi 

 are at least as old as the Devonian rocks, and it is likely that 

 they date back to that far distant time when the chief groups 

 of lower organisms were becoming differentiated after the dawn 

 of life in the primitive ocean. With their infinite variety, the 

 fungi must have possessed some of that evolutionary dri\ing 

 power which was inherent in the organisms that gave rise to 

 the dominant groups of plants and animals. It has been suggested 

 by Churchj that the growth-forms of the fungi, including the 

 lichens, are essentially those of marine algae, and he apparently 

 denies to the group any really independent power of form 

 development. For instance he states^ that "a higher fungus 

 of the land is in short a skinned seaweed, implpng a more or 

 less elaborated algal growth-form, in which in the death and 

 decay of the older metabolic and autotrophic surface layers, 

 the exposed internal heterotrophic tissues continue their hetero- 

 trophic existence at the expense of the soluble carbohydrates 

 of the standing and non-aerated medium." Where for instance 

 amongst the algae will be found the growth-forms of Xylaria, 

 Polyporns squamosus, the common mushroom, or finally of the 

 elegant Dictyophoras of the Gasteromycetes? It must not be 

 forgotten that in the higher fungi the conspicuous part is 

 essentially a spore-producing structure which cannot be directly 

 compared ^vith the somatic equipment of the algae. 



Church's view is that the fungi have been derived from 

 transmigrant algae by the loss of chlorophyll, such algae being 



* Kidston, R. and Lang, W. H. On Old Red Sandstone Plants showing 

 structure, etc. Part v. Trans. Roy. Soc. Edin. lii, p. 855 (192 1). 

 t Journal of Botany, p. 41 (1921). 

 X Church, A. H., Thalassiophyta, p. 59, etc., Oxford (1919). 



