276 



MORPHOLOGY OF GYMNOSPERMS 



cells. The latter then divides and forms two equal male cells (as 

 in Taxodium), or only two nuclei not separated by a wall (as in 

 Pinus). It is this division which among cycads and in Ginkgo results 

 in two sperm mother cells, which later produce and discharge two 

 ciliated sperms. It is this contrast in spermatogenesis that must be 





i-'r' W^ ■ 



mxm 



Wo: 



'^um 



316 



317 



318 



Figs. 316-318. — Tips of pollen tubes containing the male nuclei: m, male nuclei; 

 -//, nuclei of tube and stalk cells; s, starch; fig. 316, Pinus Strohus; June 14, 1898; 

 the body cell maintains its outline and the two male nuclei are unequal; X 236; after 

 Miss Ferguson (87); fig. 317, Pinus Laricio; the outline of the body cell is indistinct 

 and the two male nuclei are equal; Xsoo; after Coulter (44) ; fig. ^iS, Pinus Laricio; 

 somewhat later stage than that shown in fig. 317; the cytoplasm of the body cell has 

 become continuous with that of the tube; the male nuclei are equal, and above them, 

 but not shown, are the stalk and tube nuclei; Xsoo; after Chamberlain (51). 



regarded as the most important contrast between Coniferales and the 

 groups previously considered. In Coniferales a cell generation has 

 been eliminated, and whether the daughter cells of the body cell (in 

 forms like Taxodium) are called sperm mother cells or sperms makes 

 very little difference. They are formed as are the sperm mother cells 

 of the preceding groups, but they do not produce sperms; on the 

 other hand, they function as sperms, but have no cilia. These 

 non-ciliated cells, produced like mother cells and functioning like 



