272 



MORPHOLOGY OF GYMNOSPERMS 



THE MALE GAMETOPHYTE 



The male gametophyte of Pinaceae has long been known in a 

 general way, but the present knowledge of the functions of the cells 

 dates from Belajeff's work in 1891 on Juniperus (33), and Stras- 

 burger's work in 1892 on a wider range of forms, notably Larix 

 and Cupressus {t^^). Every year since has increased the number 

 of forms observed, until now a fairly complete knowledge of the 

 principal features of the male gametophyte is available. The onto- 



FiG. 301. — Pinus Laricio: part of microsporangium showing mitosis in pollen 

 mother cells, May 3; Xsoo. 



geny is comparatively uniform, so that a single account will include 

 a general outline for all forms. For this purpose, the development 

 of the male gametophyte of Pinus Laricio will be used. 



About May 9 (in Chicago) the nucleus of the microspore of P. 

 Laricio enlarges for the first division (fig. 305), a spindle is formed 

 rapidly (fig. 306), and an equal division follows. Before the cell 

 plate is organized, the nucleus nearer to the wall of the spore begins 

 to disorganize, and the other begins to enlarge (fig. 307). In this 

 way a lenticular and disorganizing cell is cut off against the spore 

 wall (fig. 308). A second division follows immediately, the spindle 

 being observed about May 25 (fig. 309). This division is a repetition 



