IO oal CHAMBERLAIN— SPERMATOGENESIS IN DIOON 225 



The blepharoplast, when nearly mature, is spherical and measures 

 16 to 18 fi in diameter. Just before breaking up into granules, it 

 becomes somewhat elliptical in section, with its longer axis parallel 

 with the longitudinal axis of the body cell. The longer axis of the 

 blepharoplast then measures about 20 p. 



THE SPERMS 



The body cell divides longitudinally, giving rise to two sperm 

 mother cells (fig. 26a). At about the time of this division, the 

 blepharoplast breaks up into a large number of granules, which at 

 first occupy the elliptical area of the blepharoplast. The granules are 



Ar.~l I _ a J 1 «• .1 • <-.T 11.1 . ~\ 1 1. 1~, , 4- -C*-^X*-^ i- V\Ck T\fWmm 



bleph 



ons between adjacent vacuoles. It is possible that granules may 



also be 

 thi 



time. The area of granules soon becomes elongated, and the 

 spiral band begins to appear (figs. 26, 26a). By this time the pollen 

 chamber has extended until it has destroyed all that part of the nucellus 

 lying above the archegonial chamber, so that there is no obstruc- 

 tion between the ends of the pollen tubes and the necks of the arche- 

 gonia (cf. figs. i 9 and 23). If the nucellus be removed, the numerous 

 Pollen tubes protruding from the pollen chamber are easily visible 

 to the naked eye, and a little later the sperms may be observed without 



PVAn +U~ • J _r , ,~ v -*• ,1 • r 4-V. Q c + or_Qh AT) PCI 



In this figure, the star-shaped 



■— "^ am ui a pocKer. lens (Jigs. 27). in uiib uguiw, ■-«. ~ — 

 area is a portion of the tissue of the nucellus, exposed by the rupturing 

 of the megaspore membrane. The evenly dotted portion represents 

 *e megaspore membrane, which in this region adheres to the nucellus 

 rather than to the female gametophyte. 



As we have said, the spiral band begins to appear as soon as the 

 a^a of granules elongates. The band is closely applied to the nucleus 

 as shown in fig. 26. The nuclear membrane is very weak in this 

 region, and the nuclear structure indicates a movement of material 

 t0 *ard the point of attachment. The connection between the nucleus 

 aQ d the band is maintained, even after the band has come to the 

 surface (fig. 28 ). In the mature sperm the band is a spiral of hve 

 or six turns, the direction being, almost without exception, from lett 

 t0 n ght, as viewed from above. The radiations, which were so 



