598 



SCIEXCE PROGRESS. 



Species. 



Period of Desiccation. 



Triticum {vul'^are ?) 

 Zea Mays 

 Raphanus sativus 

 Pastinaca oleracea 

 Daucus Carota 

 Trifolium sp. 

 Apinm graveokfts 



loi days. 



35 

 28 



14 



Frequency of Germination. 



14 times. 

 6 



5 



2 



Seeds that germinated first always supported interruption 

 best ; the effect of the latter was almost always ramification 

 of the radicle and annihilation of its geotropism. 



Ewart (9) made somewhat similar experiments with 

 peas [PisiLiii ?), to see the effect of alternate steeping and 

 drying. The seeds were spread on blotting-paper, and 

 left to become air-dried. Only one experiment was ap- 

 parently made, involving three interruptions. If the in- 

 teguments remained entire, the effect was more fatal than 

 if visible germination had commenced. Irregular develop- 

 ment of radicles was noticed. The ' vitality ' of radicles 

 was found greater than that of plumules, and often the 

 cotyledons showed more resistance than both. 



That seeds offer considerable resistance to desiccation 

 is obvious from study of the prevalent conditions in torrid 

 districts. Kerner v. Marilaun ^ states that the highest 

 temperature noticed in superficial soil of the earth 

 was at Chinoxo on the Loango Coast near the equator. 

 Here 75°C was frequently exceeded, 80° C was often 

 reached, and once 84*6° C ; annuals, however, grew on 

 entrance of the rainy season, the seeds of which had doubt- 

 less remained in the soil for months. 



Resistance to chemical agents. — A few years ago a re- 

 search of considerable interest by Cornevin (17) appeared, 

 bearing on the toxic influence of alkaloids on plants. The 

 incentive to the work was given by the theory of depen- 

 dency of immunity in animals on production of antitoxines. 

 He examined : (i.) the action of the poison of a species on 

 its own seed, (ii.) that of the same poison on seeds of differ- 



^ Pjianzenleben, vol. i., 518. 



