346 THE BIOLOGY OF FLOWERING PLANTS 



Trionum to a month in Ajuga reptans and 2 months Pceonia 

 tenuifolia. Molisch (1893) tested 26 different species and 

 found the life of the pollen grain to range from 12 days in 

 Trifoliiim hyhridum to 72 days in Narcissus poeticus. Hayes 

 and Garber (1921) state that in the maize the pollen does 

 not survive two days after leaving the anther. Anthony 

 and Harlan (1920) find that in the barley fertilisation can 

 be secured with certainty only if the pollen is transferred 

 straight from the stamen to the stigma. There are evidently 

 very great differences in this respect, and more exact and 

 extended information would be of interest, especially in 

 regard to the relative conditions in closely related wild and 

 cultivated species. 



The pollen of many plants will germinate with ease in 

 sugar solutions, on gelatine, or even in water. Rayner 

 (19 1 6) finds that the pollen of Echeveria retiisa germinates 

 in an hour in 15 per cent, sugar solution. Adams (1916), 

 in a study of the germination conditions of a number of 

 fruits, found that the pollen of the apple would germinate 

 in sugar solutions from 2*5 to 10 per cent., even after the 

 pollen had been stored for three months. That of the 

 strawberry germinated in 8 per cent, sugar, and that of 

 the olive in 16 per cent. Tischler (1917) found pollen of 

 Cassia to germinate in a 70 per cent, sugar solution. 

 Anthony and Harlan (1920) found that, while on the one 

 hand the pollen of the barley is extremely sensitive to 

 desiccation, on the other it bursts at once if placed in pure 

 water, and this seems to be the case, too, in the wheat and 

 rye. Jost (1905) found that the regulation of the water 

 supply was most important for the germination of grass 

 pollen. Martin (1913) considers that in Trifolium pratense 

 the regulation of the water supply is the most important 

 factor in securing conditions favourable to germination, and 

 that it is this relation which determines the suitable concen- 

 tration of sugar. Molisch (1893) obtained germination, in 

 sugar solution with the pollen of 12 species. Many tolerated 

 a very wide range of concentration ; Rohinia pseudacacia 

 germinated in solutions from 10 to 40 per cent., Galanthus 



