730 A TEXT-BOOK OF BOTANY. 



time required in germination will vary considerably. Many seeds 

 will germinate well within two weeks ; usually probably four or 

 five weeks are necessary. Occasionally some seeds, as with roses, 

 may require a year or two. The present tendency is to shorten 

 the period of germination in several ways. The simplest, possibly, 

 is to place the seeds in water for 24 hours. If the seed-coat is 

 more or less lignified and non-porous, boiling water is poured upon 

 them, or some special treatment may be given, as the use of dilute 



FlG. 401. Digitalis Seedlings in plant flat, three months after transplanting from 

 seed pans. These plants are now ready to be transferred to cold frames. From the Ex- 

 perimental Farm of Eli Lilly & Company, Indianapolis, Ind. 



or even concentrated mineral acids. For instance, in the culti- 

 vation of Paraguay tea or mate, for many years it was found that 

 the seeds would not germinate unless they had previously passed 

 through the alimentary tract of certain birds. Later it was found 

 that the same results could be obtained by placing the seeds in solu- 

 tions of hydrochloric acid. Miller reports that he has obtained 

 good results in the case of belladonna by first placing the seeds for 

 30 or 40 seconds in concentrated sulphuric acid. The germination 

 of seeds may also be hastened by certain mechanical means. These 

 are employed when the seed-coat is unusually thick and not easily 



