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BOTANICAL GAZETTE 



on the stigma of the same or another variety not being investi- 

 gated. Attempts were made to answer the following questions: 

 (i) what strength of sugar solution gives the most rapid germi- 

 nation; (2) how is the germination of the pollen grains affected 

 by temperature; (3) what is the rate of growth of the pollen tube; 

 (4) how long, under the most favorable conditions, do the pollen 

 grains retain their vitality ? 



Most of the following facts and figures relate to the apple, but 

 a few observations were made also on other fruits. 



Apple 



The pollen grains when dry were ellipsoidal, and comparatively 

 little variation in size was found in the varieties examined. While 

 some were longer and narrower, and others shorter and broader 

 than the figures given, the average dimensions were as follows: 

 Bramley's seedling 45X24 Wyken pippin 45X24 ix, Duchess of 

 Oldenburgh 42X27/1, Warner's King 46.5X25.5 p, Cox's orange 

 pippin 45 X 2 5 . 5 ju, Nelson 43 . 5 X 24 Bismarck 45 X 24 ju. When 

 the pollen grains were wet, they swelled up so as to become more 

 globular in shape. For instance, the pollen grains of Bramley's 

 seedling when wet measured 45X39 ju. This preliminary swelling 

 appears to be the first stage in the germination of the pollen grain. 



series 1 



For the first set of observations, solutions of cane sugar of 5, 10, 

 15, 20, 25, 30, 40, and 50 per cent strength were made. These 

 were preserved in stoppered bottles for subsequent use, but it was 

 found that after taking out a drop of the solution with a glass rod 

 and replacing the cork, an abundant growth of mycelium of Peni- 

 cillium developed in the bottles. Accordingly a fresh stock of 

 solutions had to be made, and after taking a drop out of any of 

 these the bottle was invariably brought to the boiling point. It 

 was found that by so doing the sugar solutions could be kept indefi- 

 nitely. 



As a general rule, dry pollen grains were taken from an anther 

 which had recently dehisced, and these were dusted on to a clean 

 glass slide. A drop of the sugar solution was placed on the pollen 



