THE HIGHER CUYPTOGAMIA. 419 



cells, forming two larger upper ones and two smaller termi- 

 nal cells (PI. LX, figs. 2, 2 4 .) The identity of this cellular 

 body with the compound pro-embryo which is afterwards 

 firmly inserted into the lower part of the corpusculum is 

 beyond all doubt. In Pinus Abies the germinal vesicles, 

 which remain in contact with the end of the pollen-tube, 

 regularly become clothed with firm elastic cell-membranes. 



The pollen-tube of Pinus Larix usually swells out in a 

 vesicular manner within the funnel-shaped depression of 

 the endosperm above the corpusculum, and then sends 

 forth a pointed prolongation, which pierces through the 

 covering cells of the latter. The membrane of the tube is 

 incomparably more tenacious than in the above-mentioned 

 species. In the latter when the endosperm is detached 

 from the nucleus the pollen-tube regularly tears off at the 

 place where it emerges from the tissues of the nucleus, 

 whilst in Pinus Larix the apex of the pollen-tube may often 

 be drawn out from the corpusculum, so as to hang freely 

 down for a considerable distance. 



The end of the pollen-tube even before it reaches the 

 corpusculum exhibits an accumulation of protoplasm which 

 is often sharply defined like a cell, and further upwards in 

 its interior numerous starch-granules are seen partly com- 

 bined in groups of twos or fours. Immediately after reach- 

 ing the corpusculum the apex of the pollen-tube, when 

 drawn out from the latter, appears rather thin-walled and 

 without appendages. In cones somewhat more developed 

 a cell is found fastened to the end of the pollen-tube when 

 the latter is detached. The diameter of this cell seldom 

 equals that of the end of the pollen-tube, and often re- 

 mains considerably less. It resembles in all its parts one 

 of the smaller germinal vesicles which float in the interior 

 of the corpusculum. Like these vesicles it exhibits a 

 nucleus of lighter substance, and is devoid of the firm cell- 

 membrane.* No further change is at this time perceptible 

 in the remaining portion of the corpusculum. 



* At the place where this cell is attached, the pollen-tube exhibits no trace 

 of an opening, and there is nothing to show that the cell, which differs so 

 remarkably from the pollen-tube by the absence of a firm membrane, has grown 

 out of the latter. 



