THE THREE CONDITIONS OF THE SEED 43 



range. This happens in the case of impermeable seeds where 

 the shrinking process has been incomplete, and considerably 

 less water is required for germination than in the instance of 

 the typical resting seed. 



I will first take those cases of excessive swelling displayed First, to the 

 at times by normal seeds, and will begin with permeable seeds, IwelfkiT 

 to which indeed earlier investigators seem to have mainly con- y^^'*^^^ ** 

 fined their inquiries. Dr Nobbe inferred that as a rule seeds normalseeds. 

 require to be well soaked for germination, and that those 

 cases where complete soaking is not necessary are exceptional 

 (pp. 118, 119). But he remarked that the minimum amount 

 of water needed to start the germinating process was a subject (a) By per- 

 for future inquiry (p. 120). It is, in fact, in this direction '"^*'''^^^^''^- 

 that later investigators have worked, and it is now possible to 

 distinguish between 



{a) The minimum amount of water required for starting 



germination, 

 {b) The average amount that seeds absorb under natural 



conditions in swelling for germination, 

 (c) The amount of water required for saturation. 

 The quantity of water that a seed absorbs before germinat- 

 ing under natural conditions, or in ordinary germination 

 experiments, is considerably above the minimum amount 

 needed, and markedly below the amount requisite for the 

 seed's saturation. A rough indication that leguminous seeds 

 germinate before they are saturated is found in the fact that 

 normally seeds germinate long before they rupture their coats, 

 which is the sign of the seeds being thoroughly soaked with 

 water. (I refer to ruptures taking place away from the hilum.) 

 Minimum results can, of course, be only obtained in the 

 laboratory. By an ingenious course of experiments, referred 

 to in Note 4 of the Appendix, Victor Jodin established a 

 " germinative minimum " for Peas {Pisum sativum)., and in his 

 paper he quotes similar estimates made by Van Tieghem for 

 " Ffeves " (I suppose. Broad Beans, Faba vulgaris). The results, 

 which are stated in different fashions by the various investi- 



