270 



GYMNOSPERMS 



it in embryo aflur embryo, is about as it is shown in the figure. 

 Practically all authorities say that the root cap comes from the peri- 

 blem, and it is obvious that there is no differentiated dermatogcn or 

 calyptrogen at the tip of the root. 



Fig. 276. — Root li[) of Pinus cdulis: lonRitudinul section of the root end of an embryo 

 in a ripe seed, showing a meristematic group of initials (the nuclei arc indicated), the 

 pleromc, pcriblem, and root cap; X125. 



In the root of the seedling, two protoxylem points are prevalent 

 throughout the whole group; but in the dominant genus, Pinus, 

 more than two protoxylem points are the rule (fig. 272). Pinus 

 sylveslris and P. hanksiana have diarch roots; in P. laricio and many 



