Gnetum , with some Notes on the Structure of Inflorescence . 617 
number of chromosomes appearing in the heterotypic division is probably 
twelve, as stated by Coulter for G. Gnemon } No cell-plate is recognizable in 
the course of this division. 
The homotypic division usually occurs after the isolation of the 
mother-cells. The two spindles sometimes lie approximately parallel to 
one another (Fig. 11) ; in other cases they are inclined at any angle up to 
90° (Fig. 12). Stages intermediate between these and that of Fig. 13 have 
not been seen. In the last figure, spindle-fibres are still visible, and although 
two of the three cell-plates are not continuous with the wall of the mother- 
cell (probably on account of contraction in preparation), there can be no 
doubt that the mother-cell becomes four-chambered in the same way as in 
Pinus . 2 The chambers are frequently all traversed by the same section; 
such an arrangement would follow the nuclear division shown in Fig. 11. 
The walls separating the microspores remain thin (Fig. 14) until these 
acquire their own cell-walls. Eventually they become almost as thick as 
the outer wall of the mother-cell (Fig. 15). There is nothing to suggest that 
the thickening is a second wall and not merely an addition to the primary 
cell-wall or a uniform swelling of its substance. As a rule it appears 
perfectly homogeneous in optical section. It stains faintly in Delafield’s 
haematoxylin, but it can hardly consist of unaltered cellulose. 3 Apparently 
ruptured mother-cells from which one or more of the microspores have 
escaped have been met with. But the setting free of the microspores 
appears to be more generally due to a gradual solution of the wall of the 
mother-cell, which loses its definite outline and becomes almost invisible 
while the microspores are still held in position. This suggests that the 
thickening of the wall, at least in part, and its final disorganization, are the 
result of mucilaginous degeneration. This chambering of the mother-cell 
occurs also in G. scandens , but it has not been described for Ephedra , nor 
for Welwitschia , nor for any other species of Gnetum. 
Before the disorganization of the mother-cell wall is complete, the wall 
of the microspore commences to thicken, and exine and intine are quickly 
organized. As stated by Karsten, in opposition to Strasburger, the exine 
contains no distinct pores, but is covered by minute, somewhat irregular 
protuberances (Figs. 16-20). Also, as in the species studied by Karsten, 
the microspores in a particular sporangium are not all in the same stage 
of germination at the same time. A greater degree of uniformity prevails 
in the stages preceding the organization of the microspore, but even here 
the development does not proceed pari passu in the two sporangia of the 
same flower. 
The germination of the microspore commences after it has been set 
free from the mother-cell. The spindle in the first mitosis is exceedingly 
1 Coulter (’08). 2 Ferguson (’04), p. 35, PI. IV, Fig. 45. 
3 Cf. Ferguson (’04), pp. 35, 36. 
