258 SYMBIOSIS 



us that the Monocotyledons show characters which are acquired 

 by living in water, and are in this respect just like aquatic 

 Dicotyledons, from which, he thinks, they have descended 

 " though many monocotyledons have become land plants and 

 regained all the structures necessary for an aerial existence." 



The fact of an aquatic origin would indeed go a long way to 

 account for backwardness ; for, as I have already emphasised 

 in the case of animals, they are more improved upon the land 

 because there the chances of Symbiogenesis are much greater, 

 since the land offers greater security and better opportunities 

 for the progress of socio-physiological processes than the water. 

 And, of course, what is true of animals, also holds good paripassu, 

 of the correlated development of plants. 



As an interesting instance of the degrading effect of an excess 

 of water upon plants, Prof. Henslow mentions the little sun-dew, 

 a dicotyledonous plant of the Drosera family, which 



lives in the saturated bog-moss, and has the most feeble roots possible, 

 so that it is not likely to get much nourishment. To compensate for this, 

 it has acquired the habit of, and proper structures for, catching insects 

 and so procures the necessary supply of nitrogen. It is found by experi- 

 ment to especially increase the reproductive powers, as these are very 

 sensitive to degenerating influences. 



Although this case apparently only illustrates the physical 

 effect of water, yet we have here at the same time, and in an 

 important sense, a socio-physiological effect, since there is 

 retrogression in bio-social relation. It is customary to represent 

 it as though the habitat were a matter of chance ; but in many 

 or perhaps most cases this is not so. The habitat represents the 

 choice of the organism, which, in this case, was desirous of indulg- 

 ing in in-feeding propensities, being inclined to a lazy compliance 

 with low conditions as afforded by life in, or close to, the water. 

 To say that the sun-dew cannot get much (normal) nourishment 

 because it has feeble roots, may be, and I believe is, putting the 

 cart before the horse. It is as likely as not that the habit of 

 indolent in-feeding of some kind or other has led by slow gradations 

 to a weakness and finally a degeneration of the roots. 



Darwin stated that if a plant of Drosera may be said to drink 

 by its roots, " it must drink largely, so as to retain many drops 

 of viscid fluid round the glands, sometimes as many as 260, 

 exposed during the whole day to a glaring sun," which again 

 connects the habitat with the appetites ; for it is the function 



