THE HIGHER CRYPTOGAMIA. 423 



thin layer of granular mucilage, from which fine strings 

 radiate to the Avails of the tube. In more advanced ovules 

 these cells appear to be situated nearer to the lower wall 

 of the pollen-tube, and to be fastened to the latter by an 

 accumulation of viscid protoplasm ; their earlier spherical 

 form has passed into a flatly-ellipsoidal one. Instead of 

 the central nucleus, which has now disappeared, two newly- 

 formed nuclei make their appearance, one in each focus of 

 the cell (PI. LXIII, fig. 11). 



The unimpregnated corpuscula usually contain only a 

 few (from six to ten) free germinal vesicles, amongst which 

 one in particular, which floats in the middle part of the 

 corpusculum is distinguished by its size, by the sharpness 

 of its outline, and by the richness of its granular contents 

 (PL LXIII, fig. 11)* 



The prolongation of the pollen-tube which penetrates 

 between the cells of the rosette of the corpusculum is fre- 

 quently, but not always, filled by four cells placed cross- 

 wise, manifestly produced by the twice-repeated division by 

 means of longitudinal septa of the (originally) free spheri- 

 cal cell which is now adherent to the inner wall of the 

 tube (PI. XLIV, fig. 2). One of the germinal vesicles in 

 the interior of the corpusculum, apparently the central one, 

 now appears sw r ollen, as well as more rich in granular 

 contents, and in many instances situated nearer to the base 

 of the corpusculum (PL LXIV, fig. 2). The membrane of 

 the pollen-tube when uninjured appears completely closed. 

 The openings which are sometimes seen in it after its 

 separation from the corpusculum are almost certainly acci- 

 dental ruptures. The contents of the four cells which fill 

 the pollen-tube, or of the one cell which is sometimes 

 found there, consist of very small motionless bodies, partly 

 spherical and partly spindle-shaped, which fill the cell in 

 great numbers. The next condition of the impregnated 

 corpuscula exhibits the impregnated germinal vesicle at the 

 base of the latter, firmly pressed into the lower end of the 



* In the ' Vergl. Unters.,' p. 129, I took this formation to be the primary 

 nucleus of the corpusculum. This I think was an error, because in the Abie- 

 tinefe and Juniperiuese the nucleus of the corpusculum does not last until im- 

 pregnation. 



