Gymnosperms : The Conifers 



515 



thin blade of sporophyll tissue goes with it, formmg the wing 

 of the seed. 



Summary of the conifers. In comparison with the Pterido- 

 phytes the conifers show a greatly enlarged root system, more 

 massive trunk, with numerous branches, and an internal struc- 

 ture approaching that of the dicots. The leaves have the form 

 of needles or scales which are sometimes broad, and they are 

 peculiar in being produced, not on the elongating branches, but 

 on small dwarf branches. The rate of growth of the conifers 

 far exceeds that of the cycads and ferns. The conifers likewise 

 are able to grow in almost all land habitats. 



The conifers show another step in the simplification of the 

 gametophyte generation. The cycad male gametophyte retains 

 the habit of producing swimming sperms. In the conifers this 

 habit is gone and the male nuclei pass directly from the pollen 



Fig. 322. The formation of the embryo of a pine from the fertiUzed egg (A) to the de- 

 velopment of four rudimentary embryos. Only one of the embryos will survive in the 

 mature seed. (After Buchholz.) 



