CHAPTEE XXIV 



SPERMATOPHYTES: ANGIOSPERMS 



237. Summary of Gymnosperms. — Before beginning An- 

 giosperms it is well to state clearly the characters of Gym- 

 nosperms which have set them apart as a distinct group of 

 Spermatophytes, and which serve to contrast them with 

 Angiosperms. 



(1) The microspore (pollen-grain) by wind-pollination 

 is brought into contact with the megasporangium (ovule), 

 and there develops the pollen-tube, which penetrates the 

 nucellus. This contact between pollen and ovule implies 

 an exposed or naked ovule and hence seed, and therefore 

 the name " Gymnosperm." 



(2) The female gametophyte (endosperm) is well organ- 

 ized before fertilization. 



(3) The female gametophyte produces archegonia. 



238. General characters of Angiosperms. — This is the great- 

 est group of plants, both in numbers and importance, being 

 estimated to contain about 100,000 species, and forming 

 the most conspicuous part of the vegetation of the earth. 

 It is essentially a modern group, replacing the Gymnosperms 

 which were formerly the dominant Seed-plants, and in the 

 variety of their display exceeding all other groups. The 

 name of the group is suggested by the fact that the seeds 

 are inclosed in a seed case, in contrast with the exposed 

 seeds of the Gymnosperms. 



These are also the true flowering plants, and the ap- 

 pearance of true flowers means the development of an 

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