II. Some Remarks on the Germination of the 



Pollen-mass and the Growth of the Pollen-tubes in 



Asclepias cornuti Dene. 



By 



Holger Jørgensen. 



A. 



The Formation of the Chink of the Pollen-mass in 



Asclepias cornuti and in Asclepias incarnata. 



1. 



The pollen-mass of Asclepias germinates, as is known, by 

 the formation of a chink, through which all pollen-tubes grow out, 

 in the blunt projection of the pollen-mass. 



Ehrenberg (1) and Brown (2) have first observed the chink 

 and the relation of the pollen-tubes to the same, and that the chink 

 is formed in nutrient solutions as well as in the alar chamber has 

 been proved by Brown and later by Corry (3). Both Brown and 

 Corry sought, though in vain, for some peculiarity in the wall of 

 the projection, pores or the like by which to explain the formation 

 of the chink. Neither of these investigators, the only ones, as far 

 as I know, who have been engaged about the reason of the formation 

 of the chink, have proceeded further than to search fora differentia- 

 tion of the wall of the pollen-mass. So they presumably held that 

 the reason of the formation of the chink is the penetrating of 

 liquids into the pollen-mass through the wall of the projection 

 of the pollen-mass; but they have not proved this, and even by 

 such proof the reason of the formation of the chink has not been 

 explained. 



The pollen-mass seems by its characteristic form, by the 

 manner in which the pollen-tubes issue from it, and by the dis- 

 engagement of the inner grains of pollen from each other during 

 the germination, to be a unity, where the separate grains are sub- 

 ordinated to the whole. So it will be natural to speak of the ger- 

 mination of the pollen-mass, and of the wall of the pollen-mass. As 

 the single grains of pollen, however, when isolated, which may be 



