^^os. 45^-452.] A JVA TOM V OF THE CONIFERALES. 



tendency toward a more compact disposition, while in 33.3 f the 

 cells fall into well defined aggregates or an approximation to 

 such an arrangement. The genus Sequoia is characterized 

 chiefly by the widely scattering distribution of the resin cells 

 (Fig. 40), but in .S". sempemirem there are individual cases in 

 which there is also a definite aggregation into groups. In Cu- 

 pressus 53-9'/' <>f the species are distinguished by the presence 

 of widely scattering cells which become definitely arranged in 



zones in 38.4 ^r, and aggregated into groups in 7.7'/ of the spe- 

 cies. It will be observed here that this feature of distribution 

 's, on the whole, more pronounced in the relatively primitive 

 genera, and that it diminishes in force in the genera of a rela- 

 tively high order. 



In Taxodium (Fig. 41) and Libocedrus, both of which are 

 distinguished by the presence of very prominent resin cells, these 

 structures are disposed in well defined zones which are concen- 



