202 KANSAS ACADEMY OF SCIENCE. 



an oospore has germinated and formed an embryo, which stops grow- 

 ing for a time, and then resumes it. This resumption of growth is 

 not germination, but is what happens when a seed is said to 'germi- 

 nate.' This second period of development is known as the extra-semi- 

 nal for it is inaugurated by the escape of the sporophyte from the 

 seed."^ It is this latter process that we are considering in this paper. 



Experiment shows us that certain conditions are requisite for ger- 

 mination, viz.: (1) moisture, (2) heat, (3) free oxygen. Light, 

 although essential to subsequent growth, is not requisite for germina- 

 tion. It is thought by some to impede or prevent it at the beginning. 



Germination is to a certain extent a tearing-down process ( katab- 

 olism ) ; therefore a portion of organized matter is destroyed and 

 carbonic acid is evolved. This acid is formed by the oxygen taken 

 into the seed uniting with the carbon which it contained. This is 

 most effective when one part of oxygen is diluted with three of ni- 

 trogen.^ 



The popular belief is that water is the only requisite for germina- 

 tion. This is incorrect. The amount of water differs also. As a rule 

 sufficient moisture to saturate and soften the seed is required, but in 

 certain cases germination takes place when only the radicle and the 

 albumen surrounding it have become soaked. The seeds of the 

 Leguminosse require much more water than the cereals. 



An easy experiment to prove the relation of water to germination 

 is to arrange seeds in several vessels. In one, place dry seeds on blot- 

 ting-paper that has been slightly moistened. In a second, on moist 

 blotting-paper, place seeds that have been soaked for twenty-four 

 hours. In a third, put soaked seed on saturated blotting-paper ; while 

 in a fourth put sufficient water to half cover the seeds. By placing 

 the vessels where the conditions of heat and air will be the same, it 

 will be noted that although water is a prerequisite for germination 

 yet the quantity must not be too great. 



The temperature to which seeds are subjected is an important item 

 in germination. Although the seeds of Acer platanoides (Norway 

 maple) and Triticum. vulgare (wheat) have been known to sprout on 

 ice {i. e., at 0° C.),^*^ and those of certain Alpine plants at from 0° to 

 2° C, yet there must be some heat evolved in every case. The highest 

 temperature has been found to be 50° C. Between these minimum 

 and maximum temperatures there is, according to Sachs" an opti- 

 mum, one at which germination takes place most speedily, that of 



8. Coulter, Plant Structures, p. 187. 



9. American Encyclopedic Dictionary, "Germination." 



10. Goodale, Physiological Botany, pp. 464, 465. 



11. Ibid., pp. 465, 466. 



