72 MORPHOLOGICAL DEVELOPMENT. 



where the strength required for maintaining an upright atti 

 tude is not obtained by the rolling up of the fronds, but by 

 the strengthening of the continuous mid-rib,, the second 

 frond,, so far from being less favourably circumstanced than 

 the first, becomes in some respects even more favourably 

 circumstanced : being above the other, it gets a greater share 

 of light, and it is less restricted by surrounding obstacles. 

 There is nothing, therefore, to prevent it from rapidly gaining 

 an equality with the first. And if we assume, as the truths of 

 embryology entitle us to do, an increasing tendency towards 

 anticipation in the development of subsequent fronds if 

 we assume that here, as in other cases, structures which were 

 originally produced in succession will, if the nutrition allows 

 and no mechanical dependence hinders, come to be produced 

 simultaneously; there is nothing to prevent the passage 

 of the type represented in Fig. Ill, into that represented 

 in Fig. 122. Or rather, there is everything to facilitate it; 

 seeing that natural selection will continually favour the pro 

 duction of a form in which the second frond grows in such 

 way as not to shade the first, and in such way as allows the 

 axis readily to assume a vertical position. 



Thus, then, is interpretable the universal connexion be 

 tween monocotyledonous germination and endogenous growth ; 

 as well as the similarly-universal connexion between exoge 

 nous growth and the development of two or more cotyledons. 

 That it explains these fundamental relations, adds very 

 greatly to the probability of the hypothesis. 



196. While we are in this manner enabled to discern 

 the kinship that exists between the higher vegetal types 

 themselves, as well as between them and the lower types; we 

 cotyledon does to the plumule both by position, and as a supplier of nutri 

 ment. Fig. 117, which I am enabled to add, shows that this would com 

 plete the interpretation. Of the dicotyledonous series, it is needful to add no 

 further explanation than that the difference in habit of growth, will permit 

 the second frond to root itself as well as the first ; and so to become an addi 

 tional source of nutriment, similarly circumstanced to the first and equal with it. 



