32 Principles of Plant Culture. 



placed in boiling water a few minutes before using them 

 for a second test, to destroy any spores or mycelia of 

 mold with which they may have become infected. 



39. 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, while celery 

 seed requires several days to germinate to this extent. 

 The seeds of many plants will not germinate the same 

 season they are formed, even if planted under the most 

 favorable conditions (162). 



Individual seeds of the same kind and of the same 

 sample often vary greatly in the time required for ger- 

 mination. Even in seeds that germinate soonest, as 

 lettuce and radish, some individuals will not germinate 

 until several days after the majority have germinated. 

 Seeds of tobacco and purslane* sometimes continue to 

 germinate through several successive seasons. The rea- 

 sons for these variations are not known. 



SECTION 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 above them by cover- 

 ing with a bell- jar or otherwise, for light does not hin- 

 der germination. One of the interesting facts connected 

 with germination is, that the first shoot, called 



40. The Hypocotyl* (hy'-po-co'-tyl) Grows Down- 

 ward, on emerging from the seed-case (27d), no matter 



*Pottulaca oleracea. 



