THE MORrHOLOGICAL COMPOSITION OF PLANTS. 



67 



exogenous modes of growtli ? We stall find that they do. 

 Starting, as before, with the proliferous form shown in 

 Fig. Ill, it is clear that if the strength required for main- 

 taining the vertical attitude, is obtained by the rolling up of 

 the fronds, the primary frond will more and more conceal the 

 secondary frond within it. At the same time, the secondary 

 frond must continue to be dependent on the first for its nutri- 

 tion ; and being produced within the first, must be prevented 

 by defective supply of light and air, from ever becoming syn- 

 chronous in its development with the first. Hence, this 

 infolding which leads to the endogenous mode of growth, 

 implies that there must always continue such pre-eminence 



S|C^f-5P 



4 



of tho lii'st-formed frond or its representative, as to make (he 

 germination monocotylcdonous. Figs. Ill to 115, show the 

 transitional forms that would result from the infolding of 

 the fronds. In Fig. 116, a vertical section of the form repre- 

 sented in Fig. 115, are exhibited the relations of the succes- 



