THE MORPHOLOGICAL COMPOSITION OF PLANTS. 



23 



the edges are distributed very much at random, and are by 

 no means specific in their shapes. A considerable advance is 

 displayed by PhyUophora rubens,. Fig. 39. Here the frond, 

 primary, secondary, or tertiary, betrays some approach to- 

 wards regularity in both form' and size ; by which, as also by 

 its partially- developed mid- rib, there is established a more 

 marked individuality ; and at the same time, the growth of 

 the secondary fronds no longer occurs anywhere on the edge, 

 in the same plane as the parent frond, but from the surface 

 at specific places. Delesseria sanguined, Fig. 40, illustrates 

 a much more definite arrangement of the same kind. The 

 fronds of this plant, quite regularly shaped, have their parts 

 decidedly subordinated to the whole ; and from their mid- 

 ribs grow other fronds, which are just like them. Each of 

 these fronds is an organized group of those morphological 

 units which we distinguish as aggregates of the first order. 

 And in this case, two or more such aggregates of the second 

 order, well individuated by their forms and structures, are 

 united together; and the plant composed of them is thus 

 rendered, in so far, an aggregate of the third order. 



Just noting that in certain of the most-developed Algce, as 



