1909] BRIEFER ARTICLES 71 



much longer period, a fact that led to the discovery of the temperature 

 effects. In the light of this fact, E wart's statement, "If burs are heated 

 at 40 C. for a day or two, 50 for a few hours during soaking, a variable 

 percentage of the later seeds will germinate within ten days," is not at all 



new. My 



of high temperatures 



in overcoming seed-coat effects varies greatly with different species. Further, 

 my data indicate that there is in this respect a slight variation in different 

 crops of the same species gathered from the same locality, and it appears, 

 if Ewart's data have been obtained with proper attention to sources of 

 error, that there is a decided variation in seeds gathered from different 

 regions of the globe. 



Ewart's assumption that the coats in the seeds of water plants secure 

 this delay by excluding oxygen does not seem to be true for some of these 

 species. I have mentioned evidence for this in the case of the water 

 hyacinth. 6 One of our students, working with the effects of 

 germination, tells me that seeds of Alisma Plantago germinate rather 

 readily in entire absence of oxygen, provided the coats are ruptured. In 

 the case of the upper seeds of X. canadense she finds that about 3 cm of 



oxygen 



ordinary 



necessary 



removed. These results still need to be thoroughly tested. Takahasht? 



germinate 



It is 



probable, therefore, that the coats of the seeds of water plants secure delay in 

 germination mainly by limiting the water supply, as I have pointed out. 6 

 Through a discussion of minor and less significant details, however, 

 must not lose sight of the main conclusion, which is being more firmly 



seeds 



germination 



ls generally, though not always, related to seed-coat characters rather 

 ^an to so-called dormancy of protoplasm. The coat may limit the oxygen 

 JPP y, as in the cocklebur; it may exclude or merely limit the water sup- 

 plant^ m the SeedS ° f legumes on the one hand and of Iris and other water 

 s on the other; or it is possible, though not proved, that in some cases 



necessary 



to tell f 16Ve I - am d ° ing EwART no in J u stice when I say that it is impossible 



rom his P a P er in how far it is a contribution and in how far a 



Crockei 



375-38o. ig . 



44 



7 nr 



Tokvo 6- K ^ ASHI ' T '' Is S erm ination possible in absence of air? Bull. Coll. Agr, 

 • °-439-442. 1905. 



KlCGH, G V c 



28 =8i6. i Qo8 | ; bome cas es of delayed germination in seeds. Science N. S. 



