THE MALE GAMETOPHYTE 159 



in Lilium (Strasburger, 1908), Anthericwn, and Convallaria (Geitler, 

 1935). 



Whatever the position may be, it is usually constant in individuals 

 of the same species and sometimes in all the species of a genus or 

 family and is thus a character of some systematic significance. Un- 

 fortunately, it can be recognized most clearly only in those plants 

 in which the pollen grains remain together in tetrads. In most 

 genera the microspores round up at such an early stage that it be- 

 comes impossible to distinguish one side from the other, although 

 even here the position of the germ pores and furrows often serves 

 as a useful guide. An important point to keep in mind, however, 

 is that very soon the generative cell loses contact with the wall of 

 the microspore, and after this has happened it may change its posi- 

 tion in the pollen grain and come to lie in almost any part of it. 2 



There is considerable variation in the form of the generative cell. 

 Usually it is elliptical, lenticular, or spindle-shaped, but in Cuscuta 

 (Finn, 19376) and Ottelia (Islam, 1950) it becomes long enough to 

 occupy the entire width of the pollen grain, coming quite close to 

 the inner wall of the latter on either side. In Monochoria (Banerji 

 and Haldar, 1942) it is one and a half times as long as the diameter 

 of the pollen grain and is accommodated in the latter only by the 

 incurving of its whip-like ends. In Campanula ranunculoides 

 (Schnarf, 1937) the two ends are dissimilar, one being pointed and 

 the other more or less blunt and swollen so as to look like a "head." 

 There are also occasional reports of changes in the form of the 

 generative cell. More frequently, however, such appearances are 

 merely due to the plane of sectioning. A spindle-shaped cell appears 

 round when cut across and oval when cut obliquely. 



In fixed material the cytoplasm of the generative cell is usually 

 distinguishable from that of the vegetative by its hyaline appearance 

 and general lack of food materials. Plastids (Ruhland and Wetzel, 

 1924; Krupko, 1926) (Fig. 990) and chondriosomes have, however, 

 been demonstrated in a few cases, and some recent studies on living 

 pollen grains and pollen tubes (Benetskaia, 1939; Kostriukova, 

 1939a, b; Kostriukova and Benetskaia, 1939) have confirmed the 



2 This gradual extension of the vegetative cytoplasm around the generative cell 

 and the consequent "engulfing" of the latter has been referred to by several workers, 

 viz., Friemann (1910), Wefelscheid (1911), Capoor (1937a), and others. 



