FOREST TREE SEED AND SEED COLLECTING 127 



The time required for germination is very largely determined 

 by the manner in which the seed has been stored. As a rule, 

 the drier the seed becomes in storage the longer will germi- 

 nation be delayed after seeding. Thus, walnut and hickory, if 

 stored dry, lose their vitality or else lie in the ground for a full 

 year before germinating; while, if stratified over winter, they 

 germinate the first season. 



Tests made to determine germinative capacity are seldom con- 

 tinued until all the viable seeds germinate. Bates states that in 

 District 2 germinative capacity is measured in twice the length of 

 time required to measure germinative energy. Thus, in studies made 

 on thirteen samples of lodgepole pine seed the average energy 

 period was 35 days and the capacity period 70 days. 



When a germinative test to determine germinative capacity has 

 extended over a period of from 30 to 100 days, depending upon 

 the species, it is usually closed and the viability of the unger- 

 minated seed ascertained by cutting them open. 



35. Germinative Force, Germinative Energy 



More or less confusion also exists in the use of the terms germi- 

 native force and germinative energy. They are often used syn- 

 onymously in the United States to represent the percentage of 

 germination attainable under the most favorable conditions in a 

 definite period of time. Although each of these terms has occa- 

 sionally been used by European authors with a different mean- 

 ing, the term germinative energy is now widely accepted both in 

 this country and abroad and should be used in preference to other 

 terms. Boyce 1 has recently advocated the use of the term prac- 

 tical germination per cent. 



Most experiments made to determine the germinative energy of 

 tree seed have been laboratory investigations. There are few data 

 from experiments in direct seeding or placing the seed under a 

 covering of earth in the field. In laboratory investigations the 

 seeds are germinated in ovens or in hothouses and accurate counts 

 kept of those that germinate from day to day for a period of 7, 10 

 or more days. The number of seeds that germinate during the 

 definite period of time in proportion to the whole number is the measure 

 of germinative energy. 



1 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.) 



