172 COOK 



actually bring them about. By enabling the plant to elide that 

 part of its life-history in which the delicate spore and prothallus 

 must find continuous moisture, it would deliver the primitive 

 angiosperms from the disabilities suffered by most of the ferns 

 and enable them to advance into the open sunlight. 



Young angiosperm seedlings are already of very large size 

 in comparison with fern spores, and are to that extent the better 

 able to establish themselves rapidly in exposed situations, and 

 send their roots down promptly into the permanently moist sub- 

 soil, instead of remaining dependent upon the precarious surface 

 conditions which still restrict most of the pteridophytes to humid, 

 sheltered places. 



The origin of angiosperms through apospory requires, as 

 already intimated, a less violent deviation from the normal and 

 primitive methods of sexual reproduction than that which is 

 definitely known to exist in PellcBu^ Bryophylluni and Begonia^ 

 so that no objection can be made to it on the ground of feasi- 

 bility. 



INTERNODAL METAMERISM OF ANGIOSPERMS. 



There are several morphological advantages in recognizing 

 this more simple and direct route of evolution. The first and 

 most general is that it would explain the internodal structure of 

 angiosperms, by establishing on a natural basis the complete 

 homology of all the vegetative parts and floral envelopes, the 

 cotyledons, leaves, sepals, petals, carpels and stamens. All 

 alike correspond to the same primitive structures, the capsule- 

 valves of the AntkocerosAike ancestor. 



The internodes of the angiosperms have an individuality of 

 the same kind as that of the fronds of ferns. The cotyledons 

 may be considered as members of the series of internodes or 

 joints of which each compound plant individual is composed. 

 The cotyledons are usually less different from the succeeding 

 vegetative internodes than these are from the internodes of the 

 flowers and fruits, to which the vegetative internodes finally 

 give rise. In some plants, such as Pcrsca and Pac/u'rcr, the 

 internodes which immediately succeed the cotyledons are special- 

 ized. In others, like Eucalypttis, young plants may continue for 

 a long time to produce leaves which are very different from those 



