THE MORPHOLOGICAL COMPOSITION OF PLANTS. 53 



and texture I can perceive no difference) rolled up into 

 a spherical figure." On finding in this same plant, that 

 sometimes the proliferously-produced frond buds out from 

 itself another frond before separating from the parent, 

 as shown in Fig. 46, it becomes clear 

 that this long-continued connexion may 

 readily pass into permanent connexion. 

 And when we see how, even among Phae- 

 nogams, buds may either detach them- 

 selves as bulbils, or remain attached and 

 become shoots; we can scarcely doubt 

 that among inferior plants, less definite in 

 their modes of organization, such transi- 

 tions must continually occur. 



Let us suppose, then, that Fig. 73 is 

 the frond of some primitive Archegoniate, 

 similar in general characters to Pellia 

 epiphylla, Fig. 43; bearing, like it, the 

 fructifying buds on its upper surface, 

 and having a slightly-marked mid-rib and 

 rootlets. And suppose that, as shown, 

 a secondary frond is proliferously pro- 

 duced from the mid-rib, and continues 

 attached to it. Evidently the ordinary dis- 

 continuous development, can thus become 

 a continuous development, only on con- 

 dition that there is an adequate supply, 

 to the secondary frond, of such materials 

 as are furnished by. the rootlets: the re- 

 maining materials being obtainable by 

 itself from the air. Hence, that portion of 

 the mid-rib lying between the secondary 

 frond and the chief rootlets, having its function increased, 

 will increase in bulk. An additional consequence will be a 

 greater concentration of the rootlets — there will be extra 

 growth of those which are most serviceably placed. Observe, 



