420 HOFMEISTER, ON 



In corpuscula which are about two days more advanced a 

 larger cell is seen near the end of the pollen-tube which now 

 reaches down into the corpusculum ; this larger cell differs 

 from the neighbouring unaltered germinal vesicles in its 

 circumference — which is more than double that of the latter 

 ■ — in its more transparent fluid contents, and in its firmer 

 membrane, Its upper end not unfrequently protrudes 

 above the spot at which the before-mentioned small cell is 

 attached to the apex of the pollen-tube. The large free cell 

 never exhibited any connexion with the small cell. In other 

 corpuscula of the same cone a larger cell of the same kind 

 occurs at the base of the corpusculum. Its circumference 

 is more considerable, and its contents of the same kind, as 

 in the above- described impregnated germinal vesicles of 

 JPinus sylvestris. The more pointed lower end of the oval 

 cell is filled by an oval daughter-cell with turbid contents 

 and a firmer membrane. The larger upper part of the cell 

 is devoid of a nucleus ; a thin protoplasmic layer covers 

 the inner wall, and a similar flattened layer traverses the 

 inner cavity longitudinally (PI. LXI, fig. 13). A short 

 time afterwards the lower cell, which is rich in granular 

 protoplasm, appears pressed into the base of the corpuscu- 

 lum (PL LXI, fig. 14). It is now drawn out breadthwise; 

 its upper wall, which is turned towards the inner cavity of 

 the corpusculum, is only slightly arched. Observation 

 shows that it is the rudimentary cell of the compound pro- 

 embryo. The upper unnucleated portion of the large cell 

 becomes attached laterally to the arch of the corpusculum, 

 but is soon dissolved. 



The free germinal vesicles in the upper part of the cor- 

 pusculum continue in the mean time without any observable 

 alteration (PI. LXI, fig. 14). On the other hand, the cell 

 attached to the tip of the pollen-tube becomes clothed with 

 a firmer membrane of cellulose at the time when the large 

 transparent cell appears near the tip of the pollen-tube ; 

 sometimes also it increases in size so that its transverse 

 diameter becomes three times that of the pollen-tube 

 (PL LXI, figs. 12—14). The inner wall of the pollen- 

 tube exhibits, exactly at the point where the cell is attached 

 to it, a narrow pit traversing the thickening layers which 



