GERMINATION 



excess moisture tends to weakening and damping-off 

 (78) of seedlings. 



45. Aids to germination. Most seeds properly handled 

 germinate freely; but seeds of certain families, the Um- 

 belliferse especially, are slow (parsley, carrot, celery, 

 parsnip, etc.). These and hard, bony seeds (48) allowed 

 to dry out too much may fail entirely unless treated prior 

 to sowing. Their treatment seeks to soften or break the 

 seed coats so the embryos may emerge. 



46. Enzymes used experimentally in some cases increased the per- 

 centage of germination when the seeds were soaked several hours in 

 a solution of some active enzyme or enzymes ; the vigor of the young 

 plantlets was often enhanced at the same time ; within limits these 

 good effects increase with the strength of the solution ; diastase 

 seems to be the most useful ; tomato seeds seem to respond es- 

 pecially well to diastase. 



47. Chemicals, usually di- 

 lute, or weak acids or alkalies, 

 are sometimes used for seeds 

 with hard, bony coats affected 

 neither by soaking nor freez- 

 ing. They soften the shells so 

 water may enter. Vinegar 

 aids the seeds of bramble 

 fruits (blackberry, raspberry, 

 etc.). Sulphuric acid (com- 

 mercial strength) is some- 

 times used for cotton, alfalfa 

 and clover seeds, the soaking 

 lasting two or three to 20 min- 

 utes (Fig. 21). Thorough 

 washing with water after the 

 soaking is essential. Great 

 care must be exercised in 

 diluting the acid. The acid 



into the full volume of water, but the reverse order 

 must not be followed because the acid will "fly." The 

 acid must not touch the skin or fabrics, because it burns. 



FIG. 21 KENTUCKY COFFEE 

 TREE SEEDLING 



Sulphuric acid made this develop- 

 ment in 40 days. 



may be poured slowly 



