192 BOTAXICAL GAZETTE [march 



matter of fact, I have not found as yet any essential differences 

 between the two groups; but the doubt remained that such might 

 still be discovered if it were possible to bring to germination all, or 

 almost all, the slow seeds of a given sample. For a number of 

 years I have tried various means to reach this end, but only of 

 late have I succeeded. 



It is a well known fact that many kinds of hard seeds may be 

 induced to germinate by means of filing. Filing machines, espe- 

 cially for the smaller leguminous seeds, are now often used in 

 agricultural practice, the best known one being the Swedish type, 

 constructed by Hjalmar Nilsson, the Director of the Swedish 

 Agricultural Experiment Station at Svalof. It files the seeds in 

 a continuous current by throwing them against a rapidly revolving 

 filing disk. Unfortunately, in the seeds of the evening primroses, 

 the hard layer is not the external tissue, but that of the inner 

 integimient. The outer coat thus prevents the filing, and experi- 

 ments which Professor Nilsson has had the kindness to make for 

 me with his apparatus did not give the desired result. 



In the soil the water is imbibed into the seeds through micro- 

 scopic and very narrow slits in the hard layer. It is assumed that 

 these slits are filled with air which, ip the narrower ones, is a power- 

 ful obstacle against the penetration of the water. So long as this 

 only reaches the cuticularized parts of the walls of the slits, no 

 moisture can reach the embryo and this remains dormant. The 

 question, therefore, is to compel the water to penetrate into the 

 deeper parts of the shts so as to reach the spots which can be 

 moistened. 



In order to solve this difficulty, I have tried pushing the water 

 into the slits under a high pressure. A compression of the sur- 

 rounding air to 6-8 atmospheres has proved to be sufl&cient to 

 induce all or almost all the healthy seeds to germinate in a few 

 days. The apparatus used is a combination of an autoclave with 

 an air-pump such as is used for automobiles, and the model known 

 as the Michelin pump seems to be the easiest and cheapest avail- 

 able one, while any autoclave, as, for example, an ordinary steam 

 sterilizer, will answer the purpose. Mine has 20 cm. inside diam- 

 eter, and can be filled to 8 atmospheres in about five minutes. 



