THE HIGHER CRYPTOGAMIA. 405 



In the Abietineae the lenticular daughter-cell of the 

 pollen-grain increases rapidly in size, and divides twice by 

 septa convex towards the middle point of the pollen-cell. 

 When the pollen-grain is ripe a cellular body is found 

 at one end,* projecting far into the cavity of the pollen- 

 grain, and consisting of a large vesicle borne upon a stalk 

 consisting of two low ineniscoid cells. In Pinus Larioo 

 this body fills more than half the cavity, and in Picea vul- 

 garis and Pinus sylvestris it fills the latter almost entirely 

 (PI. LIX, fig. 9). ' 



The inner membrane of the pollen-cell exhibits, even in 

 the young state, a great capacity for distension, so that 

 when placed in water the intine swells into a wide layer, 

 which stretches the extine and compresses the cell-contents. 

 After the pollen-grain is ripe this peculiarity is intensified ; 

 thus, for instance, when the detached pollen of Pinus syl- 

 vestris is moistened with water, the extine is immediately 

 ruptured, and frequently entirely stripped ofF.f 



The development of the pollen of Juniperus, Taxus, and 

 Thuja appears to be similar in all respects to that of the 

 Abietineae, but the smallness of all the parts, and the want 

 of transparency of the cell-contents interferes very much 

 with the examination in these plants. The perfect pollen- 

 grain of Juniperus, Thuja, and Taxus appears to be divided 



* That end which corresponds with the point of contact of the pollen-celi 

 with its sister-cell. In Pinus Larix the daughter-cell lies in the more pointed 

 end of the oval pollen-cell : in Pinus sylvestris arid Abies pectinata it lies on the 

 longest edge of the pollen-grain, in the middle part of that side which lies oppo- 

 site to the side which bears the two hemispherical appendages of the extine. 



f The structure of the pollen of the Abietinege was correctly understood and 

 described by Eritzsche ('Mem. Acad. St. Petersbourg p. divers savants,' III 

 (1837), p. 693). He states that at the one pole of the somewhat ellipsoidal 

 pollen-grain of Pinus Larix, the outer one of the two layers which compose the 

 inner membrane encloses a cavity filled with granular matter, underneath which, 

 in a depression of the inner layers of the intine, a second similar but more sphe- 

 rical cavity is found; to the latter is attached a closed vesicle, filled with 

 fovilla, which projects into the interior of the pollen-grain. Fritzsche in like 

 manner ascertained the structure of the pollen of Pinus sylvestris — a more diffi- 

 cult matter — only here the central vesicle appeared to him to be altogether 

 wanting. Schacht ('das Mikroskop,' 2nd edition, Berlin, 1 855, p. 148) ex- 

 plained that in P. sylvestris the vesicle in question entirely fills the cavity ; he 

 pointed out also that in the Coniferse it is not the inner membrane of the pollen- 

 grain, but the above vesicle — the terminal cell of the short row of cells which is 

 attached to one pole of the pollen-grain — which grows out and forms the 

 pollen-tube. 



