CONILKRAE: THE SCOTS PINE 541 



Comparison on the other hand with the Angiosperms shows tfa I 

 while there is a general correspondence in the propagative method, 



the balance between the alternating generations is still more lines 

 in them than in such Gymnosperms as Pinus. The germination of 

 the microspore of the Angiosperm shows only a single division prior 

 to the formation of the two gametes. But a still broader difference 

 is seen between the contents of the embryo-sac in Gymnosperms and 

 in Angiosperms : this is especially apparent at the time of fertilisation. 

 In the former the embryo-sac then contains a massive tissue of the 

 endosperm (female prothallus), with fully formed archegonia hardly 

 differing from those of some Pteridophytes (Fig. 423). But in the 

 Angiosperms it contains only the egg-apparatus, the antipodals, and 

 the central-fusion nucleus with its cytoplasm (Fig. 216). The differ- 

 ence is so wide, and the reduction of the female gametophyte so far- 

 reaching, that it is still a problem for the comparative morphologist 

 whether the several contents of the Angiospermic embryo-sac are 

 really comparable to prothallial structures. All this points to the con- 

 clusion that in the Angiosperms we see a final state of reduction of 

 the female gametophyte, the initial steps of which were taken when 

 heterospory and retention of the embryo-sac on the parent were first 

 adopted. 



The general result which follows from such comparisons is that the 

 Gymnosperms are confirmed in their position as primitive Seed- 

 Plants. This harmonises with the fact that they are represented far 

 back in Geological History. The application to them of the name 

 Archisperms appears justified. If their origin by Descent is to be 

 traced, it is to plants of the nature of the Pteridophytes that we 

 should look : and by preference to some Fern-like source. The 

 modifications which they show are all explicable as adaptations to 

 the Land-Habit. More especially is this the case in their substitution 

 of siphonogamy for zoidiogamy. With the loss of motility of the 

 spermatozoid the last direct index of their aquatic ancestry was 

 relinquished, and these primitive Seed-Plants became in the full 

 sense Plants of the Land. 



Those more recent, and still more advanced Plants of the Land, 

 the Angiosperms, owe their dominant position to their greater 

 adaptability. Its results have been illustrated for their vegetative 

 system in Chapters X., XL: and for their propagative system in 

 Chapter XIV. Ample evidence of it is also provided by the plants 

 described specifically in Appendix A. The chief features of their 

 further advance in the propagative region are seen, first, in the 



