CONIFERALES 



343 



intracellular manner. The epithelial cells of the resin canals in 

 the abietineous conifers, on the contrary, do not manifest the 

 dark-brown (so-called) "resin," but pour their secretion at once 

 into the secretory space. The secretory canals found in the case 

 of Sequoia gigantea are surrounded by cells which correspond only 

 to a very limited extent to the resin cells of cupressineous. woods. 

 Most of the secretory elements are devoid of the so-called "resin" 

 or dark-brown contents, and 

 those containing this substance 

 are present in about the same 

 proportion near the canal as 

 they are in the structure of the 

 adjacent wood. This situation 

 is clearly revealed in Figs. 249 

 and 250. 



In addition to the Taxineae, 

 Araucariineae, Abietineae, Cu- 

 pressineae, and Taxodineae 

 sub tribes of the Coniferales 

 which have been discussed to 

 a greater or less extent in the 

 earlier paragraphs of the pres- 

 ent chapter there remain the 

 Podocarpineae, a group which 

 in the present period is con- 

 fined almost entirely to the 

 Southern Hemisphere. The 

 podocarpineous forms are 



generally regarded, and with a strong degree of probability, as 

 somewhat closely allied to the Taxineae or yews, which have their 

 main distribution in the Northern Hemisphere. They are char- 

 acterized, however, by a less degree of simplification in their 

 ovuliferous cones and frequently by the possession of winged 

 pollen of the abietineous type, produced always in bisporangiate 

 microsporophylls. The organization of the female cone in the 

 Podocarpineae as a whole, and particularly in the genus Podocarpus, 

 recalls by the presence of a bract and a subtending ovuliferous 



FIG. 249. Transverse section of a 

 traumatic or wound resin canal of 



Sequoia sempervirens. 



