THE WONDERS OF LIFE 



The thallus or bed-formation consists in the simplest 

 specimens of plain or branched fine threads, consisting 

 of rows or chains of homogeneous cells (so conferva 

 among the green, ectocarpus among the brown, and cal- 

 lithamnion among the red algae). Other algae (such as 

 the ulva) form thin leaf-shaped forms of the thallus, a 

 number of homogeneous cells lying side by side along a 

 level. In the larger algae compact tissue-bodies are 

 formed, in which frequently firmer rows of cells exhibit 

 the rudiments of fibres; and the thallus divides, as in 

 the cormophyta, into root, stalk, and leaves. There is 

 also a trophic differentiation, the fibres undertaking 

 special functions of nutrition (the conduction of the sap). 

 The same must be said of the mosses (bryophyta). Their 

 lowest forms {ricciadina) are close akin to the algae; 

 the highest mosses (the mnium and polytrichum, for in- 

 stance) approach the cormophyta. Many botanists 

 comprise these lower plants — algae, fungi, and mosses^ 

 under the title of "cell-plants" (cytophyta), and oppose 

 the higher plants — ferns and flowering-plants — to them 

 as "vascular plants" (angiophyta), because they have 

 complex fibres or sap vessels. This distinction has a 

 phylogenetic significance similar to the division between 

 coelenteria and ccelomaria in the animal kingdom. 



While most of the cell-plants either live in the water 

 (algae) or are very simply organized on account of their 

 saprophytic or parasitic habits (fungi), the vascular 

 plants mostly live on land, and have to adapt themselves 

 to much more complicated conditions. Their nutrition 

 is accordingly distributed among different functions, and 

 special organs have been evolved to discharge them. 

 This is equally true of the crytogam ferns (pteridophyta) 

 and the phanerogam flowering plants (anthophyta). The 

 most important later acquisition which distinguishes 

 both groups from the lower cell-plants is the possession 

 of vascular or conducting fibres. These organs for con- 



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