STL'DIKS IN KKTAKDKI) CK KM I NATION i)?, 



The sectl trade and the technic have long made use of such i)ractiee. 

 Many hu-ge seed firms treat those seeds which are known to possess 

 "IlartschaHgkeit" before selhng them, using machines in which the 

 seed arc thrown l)y centrifugal force against the inner walls of a 

 rotating \ertical or horizontal c}'linder, these inner walls being covered 

 with a rough wearing surface. The speed of revolution and the degree 

 of roughness of the inner walls are of importance, the faster the former 

 and the greater the latter, the deeper is the seed coat injury. 'J'he 

 vertical cylinder owned by the firm of J. & P. W'issinger Company of 

 P>erlin is ordinarily run at the rate of T"JO revolutions per minute, the 

 seeds being thrown against a stationary "Schmirgel (emery) kranz" 

 \vhich runs at the ends in an iron band with cross slits, through which 

 the fallen dust is sucked ofT by means of an exhaustor and liberated in 

 the open. For larger seeds the number of revolutions must be lessened. 



The treatment of the seed coat with sulphuric acid (Hiltner process)'' 

 which produces a breaking down of the hard layer is sometimes used. 

 Lakon '' found that a two-hours soaking of Gleditsia triacanthos seed 

 caused the hard seeds to prove at once capable of germination. 



Most tree seeds excepting those of the leguminous trees, the willows, 

 birches, elms, etc., belong to group '^*' before mentioned, i.e., delay in 

 germination is the rule rather than confined to certain individuals, 

 while water and oxygen exclusion is not present. Nobbe's ' work 

 with two related wild species, Thlaspi arvense and Thlaspi alpestrc. 

 is mentioned. The seed of the latter have a delicate, gold-brown color, 

 and germinated rapidly up to 84 per cent in 14 days. The seeds of 

 T. arvense, however, of a dark brown, hardshelled appearance, ger- 

 minated 3 per cent in four weeks. This looked like a case of Hard- 

 schaligkeit, but on cutting open these seeds of T. arvense after four 

 more weeks had passed showed them to be moist and sound throughout. 

 This was also observed with seed of Euphorbia lathyris and Finns 

 Cembra." 



Delayed germination of a species calls forth two questions, (a) the 

 theoretical. TTow is this peculiar delay brought about? (7^) the prac- 

 tical. How can it be shortened ? 



The custom of some gardeners to carry seeds of certain cucurbits 

 about in ihcir pockets, e.g., cucumber seeds, in order to hasten germin- 

 ation after planting, is mentioned. It is possible that heat and moisture 

 from the body may bring this about. 



Seeds of Eu. ash, hornbeam, and late-blooming bird cherry, usually 

 require a "Keimruhe" of Ij/ years. The popular belief is that seeds 



