STUDIKS IN RKTAKDED GKRMINATION So 



attack and that the treatment of seeds with stcriHzing sohitions is of 

 great advantage, seems to he quite strongly borne out here. 



It seems possible that there is some relation ])et\veen the heavy loss 

 from soil organisms and the abundant annual seed crops of the ash 

 in particular, but also of the hornbeam. IVrliai)s the latter is a natural 

 measure to preserve the species. 



That the decay of the ash seeds in above-mentioned test proceeded 

 more rapidly than with the hornbeam seed, is probably due to the 

 thicker, firmer seed coat of the latter. Many seeds of the hornbeam 

 appeared for a time to be covered with fungous growth, but later this 

 disappeared and germination took jjlace. Many seeds of both species 

 were completely consumed within without any noticeable break in 

 the seed coat." 



The writer discusses the extent of the delay of germination in the 

 seeds which sprouted. He notes that Fraxinus excelsior requires a 

 longer "Keimruhe" than Carpinus betulus and expresses the opinion 

 that this long rest is accompanied by a lengthened danger of destruc- 

 tion by fungi. Lakon's view that the embryo of a Fraxinus excelsior 

 seed before germination must first develop to sufficient size to com- 

 pletely fill a chamber-like space between the two halves of the 

 Endosperm ^" is mentioned. Lakon holds that the enibrvo at the time 

 of ripening occupies only a part of this space and that it commences 

 growing upon being exposed to germination conditions. The writer 

 finds, however, that seeds in which the embryo has developed to com- 

 pletely fill the space were not yet able to germinate, but seem to await 

 the application of some external stimulation and he believes the 

 development of the embryo (Lakon's "Vorkermung") to be not suf- 

 ficient in itself to insure germination. As to the external stimulus 

 indicated, the writer's experience would tend to exclude mechanical 

 treatment. Yet Lakon found that sustained pressure upon the swollen 

 seeds in which the embryo within had fully grown caused a prompt 

 pushing out of the radicle. Such pressure could be brought about in 

 nature by volume changes in the overhead soil layer through alternate 

 drying out and becoming moist, by the rubbing of the seed on hard soil 

 particles, by violent air movements and b\- the running and digging 

 and crawling of animals. 



Other stimilii ^^ suggested are oxygen su]:)ply, light '- and air elec- 

 tricity.'-' Kinzel has found that light cultures of ash seed germinate 

 much faster than dark cultures. In both Fraxinus excelsior and 



