35 



Trifolium repens: Very few soods o-onuinato at 28° C, and prob- 

 ably none at 80° C. 



Mays: Probably the upper limit is 35° C, althoun:li one seed <i;er- 

 iiiinated after being exposed to 50° C. 



Melon will stand 40° C, but it is probable that above 42° C. ger- 

 mination is impossible. 



Sesamum will stand 40° C, and jmssibly 45° C., the latter being the 

 upper limit. 



These upper limits, as I have before said, depend very much on the 

 moisture, and on account of the difKculty of the experiment I have 

 not endeavored to obtain great exactness. 



Lepidium and Linum : According to the experiments of Burck- 

 hardt, some of these seeds have germinated after an inunersion of 

 half an hour in Avater at 50° C, but not after half an hour in water 

 at 60° C. 



Raphanus satirus (radish) : Lefebure shows that these seeds ger- 

 minate in moist earth at a maximum temperature of 38° C. 



Triticum (winter wheat), Triticum (spring wheat), Hordeum 

 (barley), Secale cereale (rye), and Avena (oats) germinate per- 

 fectly at 40° C, partially at 45° C, and not at all at 50° C. 



(4) The range between the maximum and min^'nium temperatures 

 at which germination is possible differs appreciably for these various 

 species. Evidently a small range is a condition unfavorable to an 

 extensive geographical distribution. 



(5) Marked diU'erences are observable between seeds of the same 

 species and coming from the same place. This is well known to the 

 farmer and strongly afl'ected some of the preceding observations. 

 The seeds of the same plant or the same capsule are not identical 

 physically nor chemically. But if the temperature and moisture are 

 those most favoral)le to germination, many seeds will sprout simul- 

 taneously, whereas near the maximum, and especially the minimum, 

 temperature the seeds germinate very irregularly and many of them 

 not at all. 



(G) The structure of the seeds, especially the presence and nature 

 of the albumen within them, ought to exert a definite influence, but 

 the small number of species that De Candolle experimented ujion 

 does not allow of extensive generalizations. 



The species/ having little or no albumen — viz, Sinap/'s, Lepidiimi, 

 and Linnm — germinate at very low temperatures. Those having the 

 next larger amounts of albumen — viz, Nhjclla, Collotiiin, and Zea 

 7)i(iys — germinate at about 5° C. ; but Sesamutn, which has l^ut little 

 albumen, requires 10° or 12° C. 



At 17° or 18° C. all these seeds germinate well, but the length of 

 time required increases somewhat as the albinnen increases, showing 

 that the latter exerts a retarding influence. The order of germina- 



