STUDIES IN POLLEN, 
WITH SPECIAL REFERENCE TO LONGEVITY 
H. E. Know.ton 
Altho much work has been done on problems concerned with pollination 
and fertilization, very little has been revealed as to the biology of the 
pollen itself. It is well known that the duration of viability of pollen 
varies with the species. It is found that corn and barley pollen only a 
few days old are unable to bring about fertilization, while date pollen 
may still effect fertilization after several years storage. The work done 
hitherto on this problem has consisted, for the most part, of mere obser- 
vations, with no study of the underlying causes of pollen longevity. Aside 
from its scientific interest, the practical aspect of the question is important. 
The viability of pollen and practical methods of prolonging its life are 
of great importance to the plant breeder. With a knowledge of the 
most favorable conditions for pollen storage, it would be possible to cross 
plants blooming at different periods or those blooming in different parts 
of the world. This would permit more extensive crossing and a wider 
scope for the work of plant improvement. 
The present work is a study of pollen and pollen longevity, with an 
attempt to determine, under different storage conditions, some of the 
reasons for pollen mortality. An endeavor was also made to discover 
practical methods of pollen storage. 
EXTENT OF STUDIES 
For a number of reasons, but particularly because it gave a fairly large 
quantity of pollen and a succession of blooms, snapdragon (A ntirrhinum 
majus lL.) was the chief material used in these experiments. The plants 
were grown in the greenhouse. For a short-lived pollen, corn (Zea Mays 
L.) was chosen. Some work was also done with apple (Pyrus malus L.). 
Since the longevity of pollen was the primary interest, only those 
morphological and physiological studies were made which seemed to have 
a direct bearing on this problem. Extensive germination tests were made, 
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