Commercial Gardening 



104 to 108 F. The best temperature, therefore, for germinating seed lies 

 somewhere between freezing-point and the last-named figures. The tem- 

 perature at which seeds will germinate most quickly is the best in all 

 cases; hence the value of ascertaining this approximately. As soon as 

 germination is completed most plants will thrive best with less heat, more 

 air and light, but particularly those seedlings whose cotyledons rise above- 

 ground and become green. 



Seeds which contain no endosperm usually germinate very quickly 

 because the embryo already contains all the reserve food within itself, as 

 in the Cabbage, Turnip, Mustard, and Willow. The Almond, Plum, and 

 Cherry take a long time to soften the hard shell in which the seed is 

 enclosed, while endosperm is absent. The seeds of many trees fail to 

 germinate at all if kept dry over the winter before being sown. If allowed 

 to get dry, the seeds of Canna often require filing and steeping in warm 

 water before they will absorb sufficient water to induce germination. 

 Carrots, Parsnips, Parsley, and Onions take a long time to germinate, 

 because the small embryo has to feed on the endosperm and grow to some 

 size before it can leave the seed. Grass seeds have a starchy endosperm, 

 but germinate quickly because the embryo is situated on the outside of the 

 mass and remains attached to it by the cotyledon while the first leaf rises 

 above-ground. The stored materials are converted from insoluble into 

 soluble matters, which the embryo can absorb. Starch is changed into 

 liquid sugar or glucose by a kind of ferment set up in the endosperm or 

 in the tissues of the embryo itself. Many seeds contain a large quantity of 

 oil, which gets changed into starch and finally into sugar, before being used 

 up by the embryo. Light is unnecessary for these processes, and is detri- 

 mental chiefly by drying up the moisture and causing great fluctuations of 

 temperature. After the seed leaves are expanded light is of the greatest 

 importance. Oily seeds soon lose the power of germination; starchy seeds, 

 like wheat and barley, and the seeds of the Pea family, which contain no 

 endosperm and little or no oil, may live for ten to forty years, but the 

 process of breathing alone would, in the course of a relatively short period, 

 consume the live substance of any seed. [j. F.] 



