BOTANICAL SUBJECTS. 183 



became fully developed by the help of insects. By absence 



of herbivorous animals at the season of maturation, these 



forms of leguminiferae had a chance of becoming disseminated. 



These forms would have a decided advantage because their 



weapon would have been two-edged. If the seed failed the 



root reproduced the plant and gave it a chance of maturing 



seed next season, and so continuing whatever advantages that 



particular variety may have accumulated. On the other hand, 



if the seed succeeded, it might not only reproduce the same 



variety, but other variations also, which might possess 



superior advantages. 



(c.) Those forms in which the flowers and seeds had been so 



perfected and their floral weapons of struggle so effective that 



they could dispense with special underground storage organs. 



The whole energy of the plant would then have been directed 



towards the perfection of the seed, and the storage tubercles 



would have become atrophied, as we see them in most 



leguminiferag (if these are atrophied tubers), or lost altogether, 



as in other plants. 



Whether these have been really the stages through which these 



interesting plants have passed is impossible to say, nevertheless, 



it is conceivable that this might have been so. It is evident from 



the great irregularity of their corolla, that insects must have been 



to a large extent their constant allies and helpers in the struggle 



for life. 



In spite of the supposed atrophy of the tubercles of the common 

 vetch (a garden weed), its underground portion retains so much 

 vitality that a bit of root left in the ground will enable the plant 

 to re -appear next season. It is not impossible that the tubercles, 

 although atrophied, may still retain some storage power. It is 

 also possible that they may have some other function unsuspected 

 by us, and the vitality of the root dependent on some other cause. 



Another view of the origin of the tubercles on the roots of the 

 leguminiferae is that primitively they werejloats in water plants. 

 The whole of our dry land vegetation must have passed through 

 a stage suited to a water life, first wholly submerged, as in 

 seaweeds, and then partially so, before the individuals became 

 suited to a wholly dry land life. And, therefore, it is conceivable 

 that the leguminous plants of to-day may have descended from 



