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



15 



was proved that the pollen-masses were able to germinate in cane- 

 sugar solutions of different strength (5 — 35 per cent), while the type 

 of germination was everywhere the same. In all the solutions the 

 majority of the pollen-tubes remained inside the pollen-mass, and 

 the pollen-tubes which succeeded in getting outside the chink, grew 

 back into the pollen-mass once more (vid. Fig. 6). 



I shall now endeavour to give an answer to 

 the question, what influence it is which the pol- 

 len-mass exercises upon the surrounding liquid, 

 an influence easy to be seen, when small quanti- 

 ties of liquid are used, though less obvious, 

 where the nutrient solution is great in quantity 

 in proportion to the pollen-mass. The question 

 is evidently not of any qualitative alteration of 

 the nutrient solution. A greater quantity of 

 liquid, in which a great number of pollen-masses 

 have been germinating is not better suited to 

 be nutrient solution than is a fresh-preparated 

 one, even as the crushing of pollen-masses in 

 a nutrient solution is of no matter to the use of 

 the latter for experiments in germination. So it 

 is an all but obvious conclusion that we have to 

 do with a quantitative alteration. At low con- 

 centrations the pollen-tubes do not get very 

 long before bursting, the less liquid the pollen- 

 mass is placed in, the longer they become, at 

 higher concentrations they get still longer before bursting, and 

 by letting the concentration of the liquid, in which the pollen-mass 

 is placed, rise highly, the bursting of the pollen-tubes may be al- 

 together avoided, though the development of the pollen-tubes 

 will generally be stopped at the same time. If we contemplate these 

 facts and the other conditions of the pollen-mass, starting from the 

 theory of the osmotic pressure, we must conclude that the alteration 

 of the liquid, effected by the pollen-mass, an alteration which 

 makes the pollen-tubes grow, consists in the concentration of the 

 liquid being made to rise, and as the transfer of pollen-masses 

 from one concentration to another in greater quantities of liquid 

 is of no consequence to the growth of the pollen-tubes it is moreover 

 to be concluded that this rise must proceed quite smoothly. 



Accordingly I will explain the conditions of the pollen-tubes 

 in culture in the following manner. I. The pollen-tubes need in 

 order to grow a particular external stimulus. This stimulus presumably 



Fig. 6. 

 Pollen-mass which 

 has germinated in 

 10 ccm. of a 30 

 per cent cane-su- 

 gar solution. The 

 same germination 

 in greater quan- 

 tities of cane-sugar 

 solutions the con- 

 centrations of 

 which are between 

 10 per cent and 

 35 per cent. X '25. 



