288 BOTANICAL GAZETTE [april 



to be the fertilization nucleus. At that time Belajeff (6) showed 

 that in Taxus baccata the larger cell is not the generative cell; but 

 that the small cell divides in the tube and one of the derivatives 

 becomes the generative cell. 



In 1892 Strasburger (i) described Ginkgo biloba as having two 

 prothallial cells, representing a vegetative prothallus, and an 

 antheridial cell, which are successively cut off from the pollen 

 cell; the antheridial cell divides into stalk and body, the latter 

 produces the sperms. The large pollen nucleus, because of its 

 foremost position in the tube, was called the tube nucleus. The 

 general conception of origin and function is the same today. It is 

 not surprising, however, that, with such a variety of types, different 

 investigators have since used different terms to designate similar 

 cells. 



The system of nomenclature to be used in this account has been 

 made necessary by the nature of the gametophytic development. 

 The primary cell (P) is regarded as retaining its identity, just as 

 an apical cell. In the pollen tube stages it is represented by the 

 tube nucleus. The successive divisions of the primary nucleus are 

 known as primary divisions; the cells cut off are called, tentatively, 

 the first, second, or third primary derivatives (a', a", a'" in figs.). 

 Divisions of the latter cells are called secondary. The cell which 

 later divides to form male nuclei is termed spermatogenous (s in 

 figs.); the sister non-functioning cell is the sterile cell (5/ in figs.). 

 The mother cell of a spermatogenous and a sterile cell is called an 

 antheridial cell. 



Development of the male gametophyte 



The first primary division is variable; the cell wall may cut 

 off a lenticular polar cell (fig. 7) ; it may be oriented at right angles 

 to the longitudinal axis, cutting off approximately one-third of 

 the protoplasmic mass (figs. 6, 33, 37, 53); it may be in the plane ' 

 of the vertical axis, in which case two nearly equal cells result 

 (figs. 2, 10, n, 13, 31, 32); it is often inclined (figs. 28, 29); and 

 occasionally no dividing wall is formed, the two resulting nuclei 

 being then free in the cytoplasmic mass (figs. 8, 9, 12). The further 

 development of the resulting cells is largely determined by the 



