CONIFERALES 



107 



there are at least two great divergent families of Conifers, the 

 Taxaceae and Pinaceae, differing from each other not only in 

 certain important morphological characters, but also in general 

 geographic distribution. 



The Taxaceae are characteristically south temperate forms, 

 and include only about seventy-one species. Generally true 

 strobili are not organized, at least they do not conceal the ovules, 

 vi^hich are freely exposed. This would seem to diminish the 

 chances of pollination as compared with the arrangement in 

 Pinaceae, where the scales are of some service in catching pollen. 

 Moreover, the seeds always develop a partially fleshy testa or 

 an aril, which seems to be corre- 

 lated with their exposed con- 

 dition. 



The Pinaceae, on the other 

 hand, are characteristically north 

 temperate forms, and include 

 about two hundred and twenty- 

 four of the two hundred and 

 ninety-five known species of Con- 

 ifers, and in individual or forest 

 display the difference is much 

 greater. Some explanation of 

 this more favorable adaptation 

 to present conditions may be 

 found in the fact that the organ- 

 ization of true strobili not mere- 

 ly protects the ovules, but also 

 increases the chances for pollina- 

 tion. In the maturing of the 

 seed the testa is woody or leath- 

 ery, with no fleshy development, 

 such as is characteristic of Cycads 

 and Ginlcgo, and of the Taxaceae, 

 not even in the form of a fleshy 



aril. "With such characters, and also with the northern distribu- 

 tion, the Pinaceae stand out quite distinctly. 



The Taxaceae, with their exposed ovules and succulent seed 

 investment, contain but eight of the thirty-five genera of Coni- 

 fers, and only seventy-one of the two hundred and ninety-five 



Fig 82 — Pmus Lcuficio, longitudinal 

 section of the ovule bhowing the be- 

 ginning of the testa (shaded zone) : 

 *, integument ; ^, pollen tubes ; n^ 

 nucellus ; u, arohegonium ; g, endo- 

 sperm ; f, testa ; x 14. 



