THE HIGHER CRYPTOGAMIA. 417 



cavity of the corpusculum, by being somewhat larger, and 

 especially by its containing a considerable quantity of 

 granules of protoplasm of a larger size (PI. LXII, fig. 2). 

 The nucleus of these cells differs from those of the neigh- 

 bouring germinal vesicles by the more considerable size of 

 the nucleoli. In other corpuscula which were taken partly 

 from ovules of the same cone I found a similar cell, 

 but without a nucleus, at the base of the corpusculum. In 

 other corpuscula, again, from the same inflorescence, a cell 

 of the same kind furnished with a firm membrane * was 

 firmly pressed into the lower end of the corpusculum. It 

 can now be recognised beyond a doubt as the primary cell 

 of the compound pro-embryo (PI. LXII, fig. 4). In an 

 impregnated corpusculum of Pinus canadensis which 

 already contained a multicellular pro-embryo, I once saw a 

 large free cell, situated above the latter and containing two 

 nuclei, and very similar to an impregnated germinal vesicle 

 on the point of dividing (PL LXII, fig. 5). This observa- 

 tion is the only one of the kind which occurred in the 

 course of my very numerous investigations, and it indicates 

 that more than one germinal vesicle of the same corpus- 

 culum may be impregnated. 



The pollen-tube of Pinus sylvestris, after penetrating the 

 rosette of the corpusculum, usually passes only for a short 

 distance into the interior of the latter, so that the end of 

 the tube projects into the end of the cavity in a hemi- 

 spherical form ; a farther penetration is of rare occurrence. 

 In the earliest observed conditions in which a change in the 

 contents of the corpusculum was perceptible, an oval, capa- 

 cious, sharply defined cell, was visible near the base of the 

 corpusculum ; in the more pointed lower end of this cell a 

 lenticular nucleus was embedded in a considerable accumu- 

 lation of granular protoplasm (PI. LX, fig. 9). The walls 

 of the upper part of the cell are clothed with a thin layer 

 of plasma ; a flattened layer of protoplasm passes through 

 the entire length of the upper cavity of the cell. In other 

 corpuscula the lower end of this cell almost touched the 

 base of the corpusculum. In these cases the nucleus, and 

 the accumulation of protoplasm enclosing it, appeared sur- 



* In the conditions previously mentioned this membrane was wanting. 



27 



