26 MORPHOLOGY OF SPERMATOPHYTES 



vegetative cell and the generative cell, the former actively push- 

 ing in the v^^all of the latter until there is an appearance of one 

 cell within another. It is at this stage that Ikeno observed the 

 tube ptishing into the nucellus and carrying with it the tube 

 nucleus, after which the generative cell divides to f orin the two 

 cells whichhave been called the stalk cell and the body cell. In 

 Cycas, as in Ginkgo, the plane of this division is at right angles 

 to the former planes of division, so that the stalk and body cells 

 lie side by side and are equally free to develop further. In 

 Zamia, however, as xisually in Pinus, the plane is parallel with 

 the former ones, and the two cells lie fore and aft — that is, in a 

 lineal series with the vegetative cell. It is this position which 

 seems to have suggested the name stalk cell for the one next 

 to the vegetative cell. 



The stalk cell functions no further, but the body cell enters 

 upon the history which is of greatest interest in the investiga- 

 tions of Ikeno and Webber, paralleled by Hirase for Ginkgo. 

 Bodies appear, named hlepharoplasts by Webber,^^ one at each 

 pole of the nucleus, their final position being in an axis at right 

 angles to the long axis of the pollen tube. The origin of these 

 bodies is unknown, but nothing to suggest them occurs in any 

 other cells of the plant. In their polar position they develop 

 remarkably in size, reaching a diameter of 10 to 15 /i in Cycas 

 and 18 to 20/a in Zamia, and giving off fibers which seem to join 

 with the very evident cytoplasmic network. 



In the meantime the pollen tube, containing the tube nucleus, 

 has been growing through the nucellar tissue, and branching 

 more or less freely, but apparently not so profusely as in Ginkgo. 

 It seems to function only as an absorbing organ, for the male cells 

 never pass into it. A short time before fertilization the tube 

 nucleus passes back through the tube and consorts with the stalk 

 and body cells, after which the body cell di\ddes. 



This division occurs in a plane at right angles to the axis 

 connecting the much-enlarged hlepharoplasts, and results in the 

 formation of two male cells, morphologically sperm mother cells, 

 ■which lie side by side, their free faces rounded, and each with a 

 single blepharoplast. The blepharoplast breaks up into a group 

 of granules, and in Cycas, according to Ikeno, a beaklike process 

 which remains closely associated with the blepharoplast granules 

 is put out from the nucleus. The elongating beak and granules 



