THE PRINCIPLE OF COHESION. 



73 



central, has given rise to a good deal of discussion. Two 

 views have been taken, one being that such ovules are, in 

 some cases at least, axial in their origin, and not carpellarj at 

 all ; others would refer all ovules, without exception, to a 

 carpellary source. Analogy, indeed, would, if taken alone, 

 seem to justify the latter conclusion, since the numerical 

 proportion of ovules having a decidedly carpellary origin is 

 unmistakably very great; and any doubt upon the matter 

 seems to me to have arisen from a want of due appreciation 

 of the arrest of development, or rather failure of a complete 

 differentiation which has taken place between the ovary and 

 axis at the place where the ovule or ovules appear. 



This arrest is particularly apparent, as already stated, in 

 the case of inferior 

 ovaries, as of the Ivy. 

 Thus, in the Compositfr, 

 the ovular papilla seems 

 to arise at the base of a 

 cavity in the axis, and 

 might easily be thought 

 to be axial ; but a slight 

 eccentricity may be dis- 

 cerned at a certain epoch 

 which is the first indica- 

 tion of its carpellary 

 origin. In Beta the 

 basal ovule arises in a 

 very similar manner, 

 but as the ovary becomes 

 more developed, the 

 ovule is carried up so 

 as finally to become pendulous (Fig. 16, a, b, c.) It is 

 much the same in Typha and allied genera. The same 



Fig. 16.— Beta (after Payor). 



