CHAPTER III 

 The Genesis of the Typical Forms of the Plant Kingdom 



IF the ingenuity of the naturalists has been tirelessly exer- 

 cised on all matters relating to the problems of variability 

 in living forms, it has turned aside from any explanation of 

 factors which are fixed and stable. All variations of detail have 

 been studied with the most painstaking care ; botanists have 

 been at the greatest pains to note the slightest modifications 

 in the form and colour of flower-petals, in the contour of leaves, 

 in the abundance or scarcity of hairs ; they have made careful 

 and sometimes ultra-minute distinctions in the case of Briars 

 and Vines, for instance, between species and sub-species ; 

 between spontaneous, geographic or merely topographic, 

 cultivated or wild races, varieties and sudden, heritable 

 variations, fluctuations, etc. The zoologists have been 

 hardly less energetic in studying the smallest variations. They 

 have made violent onslaughts upon the old classification — 

 striped, spotted and piebald animals, and have even sub- 

 divided the African Elephants, because their ears and 

 tails are not exactly alike. Interesting as it may be to 

 study the variability of details, all this is certainly not 

 so important as the causes that have led to the development 

 of animals and plants on the lines of those marvellously 

 persistent types which Cuvier called embranchements (main 

 divisions) ; or as the reasons for differentiation between 

 plants and animals. 



The latter question has been broached before. Plants take 

 their special character from the fact that every one of their 

 essential parts is enclosed in a rigid cellulose membrane, 

 preventing any movement and consequently any external sign 

 of sensibility. This membrane may temporarily be missing, as 

 in the case of the zoospores and the antherozoids or 

 reproductive cells of certain algae and fungi. It may only be 

 present for a time, and then only around the spores or repro- 

 ductive cells, as in the case of slime-fungi or Myxomycetes, 



