Holger Jørgensen: The Germination of the Pollen-mass etc. 9 



obvious in this species that the chink is made on account of turgor 

 in the grains of pollen, as the protoplasm of the grains of pollen, in 

 whose walls the chink is formed, is squeezed through it immediately 

 after its formation (vid. Fig. 1). 



In the Asclepias cornuti the chink is not formed until long after 

 the liquid, in which the pollen-mass is put, has penetrated, so that 

 all the grains of pollen become turgid, before the bursting takes 

 place. 



Our object is now to show, why only the grains of pollen, that 

 form the projection of the pollen-mass, burst open their free surface, 

 while the rest of the grains of pollen, which help to form the surface 

 of the pollen-mass, send their tubes into the pollen-mass, and from 

 this out through the chink. 



2. 



Brown arid Corry assumed there being some peculiarity in 

 the wall of the pollen-mass of the projection, and, in fact, there is 

 a difference between the wall of the projection and the rest of the 

 wall of the pollen-mass. This difference may be made 

 visible by dyeing with aniline dyes. If we examine a pol- 

 len-mass, which has been lying only a few moments in a 

 safranine or some other solution of aniline dyes (of other 

 aniline dyes I have tried neutral red, methyl green and 

 methyl blue and all gave the same result) it will be seen Yig. 2. 

 that the wall of the projection has been dyed intensively, 

 while the rest of the wall of the pollen-mass has not yet become dyed 

 (vid. Fig. 2). Only on remaining in the solution of colour for a longer 

 time, the whole of the wall of the pollen-mass is dyed. From the 

 wall of the projection, the coulouring-matter soon enters into the 

 pollen grains within, and hence into the pollen-mass, of which fact 

 we may convince ourselves by crushing the pollen-masses, which 

 have been lying in the solution for a shorter or a longer time. Thus 

 the wall of the pollen-mass of the projection proves to absorb ani- 

 line dyes sooner, and to let them pass through more quickly, than 

 does the rest of the wall of the pollen-mass 1 ). 



I shall here take the opportunity of mentioning a few reactions of co- 

 lour in the wall of the pollen-mass. In bases the wall of the pollen- 

 mass is dyed a reddish-brown ; the colour disappears again in water, 

 and more rapidly in dilute acids. In strong sulphuric acid the wall of 

 the pollen-mass becomes a deep red. The colour disappears in a weaker 

 acid and in water, but reappears on the pollen-mass being replaced 



