162 WHAT IS A PLANT? 



pendently of both these agents, so long as the food is other than 

 carbonic acid. 



Again. Torula, the yeast-organism, the one causing fermenta- 

 tion in sugary solutions, flourishes, if placed in a tartrate liquid ; 

 but — and mark this — it flourishes far more abundantly if pepsin, a 

 nitrogenous body, be added. Here it seems to feed on ready- 

 made protein, like an animal, and we see no reason to doubt that 

 Botrytis and Enipusina^ the fungi, respectively, of the caterpillar 

 and the house-fly, Peronospoi-a^ the potato-fungus, Ile?jiileia, the 

 coffee-plant fungus, Piicciniuin^ parasitic on grasses, and ^cidmni, 

 living on the celandine, as also the Fungi that are parasitic on 

 human skin, do, one and all, feed on the ready-made protein of 

 their hosts. Thus they resemble animals, although undoubtedly 

 plants. 



^fhaliiu/i, or flowers-of-tan, an organism growing around tan- 

 pits, during part of its life has no cellulose coat, feeds on protein, 

 takes in solid food, and moves about from place to place, even 

 going so far as to chmb some little way up the trunks of adjacent 

 trees ; yet, at another period, it shows several distinctly plant- 

 features. It is, at present, a biological puzzle. The organisms 

 known as Monads — such as the " Heteromita " of Huxley and the 

 "" calycine monad " of Dr. Dallinger — are equally puzzling. The 

 latter is an organism only one three-thousandth of an inch in size, 

 possessing two cilia, the hinder one being only one one-hundred- 

 thousandth of an inch in diameter ! These bodies resemble 

 plants in many ways, and yet may with almost equal reason be 

 placed among animals. We cannot say which they may be until 

 their method of feeding has been definitely ascertained. Finally, 

 there are the Insectivorous plants — Drosera, etc. — that feed on the 

 nitrogenous compounds of their victims. 



On the plant side, therefore, modifications are by no means 

 few or inconsiderable ; but even on the animal side, where the 

 absence of power to manufacture is very nearly universal, Mr. 

 Geddes has found that in Convoluia * fine granules of starch are 

 formed inside its green chlorophyU granules, looking as if the 

 creature were nourished in virtue of its chlorophyll — /.(?., as if it 

 fed on carbonic acid, like a plant ; and we are by no means sure 

 * Vide No. IX. in this paper, "Gas-Exchange." 



