GERMINATION 41 



The depth to which the seed should be planted depends 

 partly upon the porosity of the soil and partly upon the size 

 of the seed. (3) Prevent the caking of the soil, which is 

 usually caused either by repeated waterings or by allowing 

 the soil to dry out too quickly. 



Temperature Necessary for Germination. — There is a wide 

 range of temperature at which the many kinds of seed 

 will germinate. The proper temperature depends primarily 

 upon the constitutional peculiarities of the seed. Some seed 

 will germinate close to the freezing-point and often they may 

 be repeatedly frozen and thawed without this process causing 

 harmful results. Rye gives a fitting example. The seed 

 of this plant can be germinated on cakes of ice, and seemingly 

 experiences no great difficulty in growing. However, this 

 is an exceptional example, and many other seed, which 

 include by far the greater number of species, fail to germinate 

 unless the proper temperature is maintained. 



There are three degrees of temperature recognized for the 

 germination of seed: (1) minimum; (2) optimum; and (3) 

 maximum. The minimum temperature is the lowest tem- 

 perature at which a seed will germinate. The maximum 

 is the highest temperature at which a seed will germinate. 

 The optimum is the medium temperature between the 

 minimum and the maximum. The optimum is the best 

 temperature at which to place a seed for proper germina- 

 tion. The optimum temperature is not a stationary tempera- 

 ture but it fluctuates up and down, due to the species, 

 the difference in vigor, the ripeness and the general condi- 

 tions of the seed in question. 



There is no way of very accurately controlling the tempera- 

 ture out of doors. The depth of planting is the only practical 

 means of regulating the temperature to any degree, and this 

 only slightly. This also influences the degree of moisture 

 in the open ground as well as the temperature. However, 

 there is a direct influence upon the essential growth oi the 

 plant determined by either deep or shallow planting. A 

 seed can be planted much deeper in a light soil than in heavy 

 clay soil. It can also be planted deeper late in the season 

 than early in the season. The seed must not be planted 



