32 Principles of Plant Culture. 



subtracting the number tliat fail to sprout from the num- 

 ber put in, the per cent of ^'itality may be readily com- 

 puted. The cloths should l)e placed in boiling water a 

 few minutes before using them for a second test, to de- 

 stroy any spores or mycelia of mold with which they 

 may have bec(mie infected. 



40. The Time Required for Germination varies greatly 

 in different kinds of seeds. In lettuce seed, the tiny 

 white shoot often breaks through the seed-case within 

 twenty-four hours from planting, ^'hile celery seed re- 

 quires several days to germinate to this extent. The 

 seeds of many plants will not germinate the same season 

 thej are formed, even if planted under the most fa^'or- 

 able conditions (163). 



Individual seeds of the same kind and of the same 

 sample often vary greatly in the time required for ger- 

 mination. Imcu in seeds that germinate soonest, as let- 

 tuce and radish, some individuals will not germinate 

 until several days after the majority ha\'e germinated. 

 Seeds of toljacco and purslane* sometimes continue to 

 germinate through several successive seasons. The rea- 

 sons for these \'ariations are not known. 



Sectiox III. The Plantlet 

 By watching the germination of seeds, we may learn 

 some interesting facts. Viable seeds will usually germi- 

 nate freely on the surface of well-moistened soil or sand, 

 if we provide a damp atmosphere abo\'e them by C(i\'er- 

 ing with a bell -jar or other\i ise, for light does not hinder 

 gei-mination. One of tlie interesting facts connected 

 with germinati(jn is, that the first shoot, called 



