8 Dansk Botanisk Arkiv, Bd. 2 Nr. 10. 



effected by cutting the pollen-mass, germinate just as well as when 

 they are in the pollen-mass, the latter must principally be regarded 

 as a group of grains of pollen which have however remained so 

 coherent as to have kept common walls. Thus the form of the pollen- 

 mass is due to the grains of pollen being arranged in a characteristic 

 manner, and the wall of the pollen-mass is in reality nothing but a 

 mosaic of the walls of the grains of pollen. Consequently the chink 



Fig. 1. 

 A. The part of the pollen-mass of Asclepias incarnata, in which 

 the fissure is formed, shortly after the pollen-mass being put 

 into water. B. Pollen-mass of Asclepias cornuti with its fissure. 

 Here, as in the following Figs., the walls between the grains of 

 pollen have been left out. 



must be taken to be a bursting of the outer walls of the grains of 

 pollen that form the projection. After the bursting, the pollen-tubes 

 of these grains grow out through the chink thus formed. During 

 the germination, the inner grains of the pollen-mass gradually detach 

 themselves from one another, so that all the grains of the pollen- 

 mass may send their pollen-tubes out through the chink. 



The chinks being formed by bursting is already seen by the 

 fact that its edges are quite keen (vid. Fig. 1), and further it is seen 

 quite clearly in the closely related species, Asclepias incarnata; for 

 in this species the chink is formed so to speak instantaneously on 

 the pollen-mass being put into water. At the same time it is quite 



