FOREST TREE SEED AND SEED COLLECTING 125 



Rafn, Bates, 1 and others for the same purpose. As germination 

 per cent is sometimes employed to express germination in a given 

 length of time, it should not be used to express the total percent- 

 age of germination irrespective of time. Boyce 2 has suggested 

 the term final germination per cent to represent this proportion. 

 The author believes the term germinative capacity is the most 

 desirable of these terms, meets with most general acceptance, 

 and should be used in preference to the others. 



34. VARIATION IN THE GERMINATIVE CAPACITY OF FRESH SEED 

 The germinative capacity of fresh seed depends upon : 



a. The species. c. The individual. 



b. The season. d. The locality. 



Under the best conditions some species, as illustrated in hem- 

 lock, bald cypress, basswood, sycamore, and tulip, produce seed 

 that average extremely low in germinative capacity. Less than 

 5 per cent of tulip seed on the average is fertile. Many species, 

 on the other hand, average high in germination. When pine and 

 spruce seed is fresh a germinative capacity of from 80 to 95 per 

 cent is not unusual. 



A wet spring is often the cause of a large number of blind seed or 

 those otherwise imperfectly developed. A dry summer causes the 

 seed to be small and the seedlings grown from them weak and 

 inferior. A severe drought in August and early September ruins 

 the chestnut crop in southern New England. In cases where 

 none of the egg cells within the ovules become fertilized, the fruit 

 with its contained seed fails to develop. Cold, wet weather at the 

 time of pollenation checks the flight of insects and prevents the 

 pollen from being carried by the wind. As a result, pollenation 

 does not take place, and consequently the embryo fails to develop. 



Trees growing at the limits of their range or otherwise in un- 

 favorable localities usually produce a high percentage of infertile 

 seed. In many instances all seeds are sterile. For this and other 

 reasons relating to environment, age, and condition of the indi- 

 vidual, seed collected from one tree may have a much higher 



1 Bates, C. G.: The technique of seed testing. (Proc. Soc. Am. For., 

 vol. VIII, pp. 127-138. 1913.) 



2 Boyce, I. S.: Some methods in the germination tests of coniferous tree 

 seeds. (The Forest Club Annual, University of Nebraska, vol. VI, p. 72. 

 1915.) 



