Mr. W. M. Holmes on the Nutrition of Plants. 157 



is exposed to show the arrangement of the hymenium or spore- 

 bearing membrane in gills, pores, spines, &c., it is difficult even to 

 guess to which genus the fungus belongs. Other species in the 

 same genera have a different form : some with a central stem ; 

 others resupinate, i.e., spread out over the surface on which they 

 grow. 



Among exotic plants still more striking examples might be 

 obtained. Thus the Cactaceae, with their leafless succulent, 

 often spiny stems, are counterfeited on the one hand by the 

 Stapelias, on the other, as already mentioned, by the succulent 

 species of Euphorbia. 



The Cycads, palms, and tree-ferns — plants widely separated in 

 a systematic arrangement — alike present the simple erect stem 

 surmounted by a terminal bunch of large feathery leaves which 

 forms so characteristic a feature in tropical forest landscapes. 



But my botanical knowledge or your patience would fail, 

 rather than the number of available examples, if I attempted to 

 multiply instances in which plants in nowise closely related 

 to each other, in order to fill similar positions in the physical 

 world, have undergone adaptations on parallel lines. 



119. — The Nutrition of Plants. 



By W. Moeton Holmes. 



(Read December 18th, 1894.) 



There is perhaps no subject which engrosses so much general 

 attention as the subject of eating and drinking. Directly or in- 

 directly the whole fabric of society is based upon the food-supply. 



We are all conscious — sometimes painfully conscious — of the 

 necessity of taking a due supply of nourishment, and we concede 

 without question that other members of the animal kingdom 

 have the same need. But we do not always consider that plants 

 have similar requirements. The only idea of the average rnan 

 — or woman — concerning vegetables is that they are something 

 to be eaten, and any further thought as to nutriment ceases. 

 Nevertheless plants work indefatigably for their living. 



A living plant, whether consisting simply of a single cell or of 

 a large number of cells in combination, takes up food from its 

 surroundings according to its immediate needs. The method of 

 absorption varies considerably, depending upon the nature of the 

 nutriment, differences of habitat, requirements of particular 

 species, and the constitution of the protoplasm in each species 

 concerned. 



