THE HIGHER CRYPTOGAMIA. 421 



in the mean time have been deposited upon its wall (PI. LXT, 

 fig. 12). This pit always appeared to be closed on the out- 

 side by the primary membrane of the pollen-tube ; no open 

 communication between the pollen-tube and the cell could 

 be ascertained. The nucleus of this cell has by this time 

 disappeared ; its contents, which are tolerably transparent, 

 are only rendered turbid to a certain extent by a few fine 

 grannies. Sometimes it contains some larger bodies, equal 

 in size to the starch granules in the pollen-tube, and com- 

 posed of a substance rendered brown by iodine. The 

 relations of position between the cell and the pollen -tube 

 are of two kinds: either the upper part of the cell is 

 attached to the terminal point of the extended conical tip 

 of the pollen-tube, and thus hangs down freely into the 

 cavity of the corpusculum (PI. LXI, figs. 13, 14), or else 

 the end of the pollen-tube is lifted up round the cell — so 

 as to form an annular cushion — and grows round the larger 

 part of the cell so as only to leave the hemispherical lower 

 end protruding out of the introverted end of the pollen- 

 tube (PI. LXI, fig. 11). This process has been observed 

 in its different stages. If a moderate pressure is applied to 

 the upper end of a pollen-tube having the attached cell 

 enclosed in the introversion of its apex (PL LXI, fig. 11), 

 the introverted membrane often becomes exserted, and the 

 exserted portion then appears to be conical, and bears the 

 cell in question at its outermost tip (PL LXI, fig. 11), just 

 as in the first case above described. The two forms of the 

 end of the pollen -tube are equally common in longitudinal 

 sections of corpuscula. In isolated instances two such cells 

 are attached to the tip of the pollen-tube. 



Prom these observations on the Abietinese I think the 

 following conclusions may be drawn as to the development 

 of the embryo. After the arrival of the end of the pollen- 

 tube at or into the upper end of the corpusculum, one of 

 the germinal vesicles lying near the end of the pollen-tube 

 is impregnated. It increases in size, and glides through the 

 mass — consisting of protoplasm and unimpregnated germi- 

 nal vesicles — which fills the corpusculum, down to the base 

 of the latter, into which it presses itself. At this time (in 

 Pinus canadensis) or, (in P. syhestris and Lariso) even 



