PROPAGATION OF PLANTS 



149 



still the results obtained in sowing may be somewhat unsatis- 

 factory. Correct size, form, color, and odor are not always suf- 

 ficient to insure the germination of the seed that we sow. When 

 the results under such conditions still prove disappointing, the seeds 

 are lacking in vitality. The things that affect the vitality of seeds 

 are as follows: (1) the maturity of the seed; (2) the vigor and gen- 

 eral condition of the parent plant; (3) the age of the seeds; (4) the 

 method of their preservation or the proper conditions of storage. 



Maturity. The significance of after ripening for the formation 

 of perfect seeds cannot be overestimated, and there can be no 

 doubt that dead ripe seeds are the best for sowing. This is 

 clearly shown in the experiments made by Hellriegel. He selected 

 a number of rye plants, from a good field of this grain, at five 

 different periods of maturity. The first sample of seed was taken 

 when both plant and grain were still completely green and the 

 seeds were small and watery. The second sample was secured 

 when the plant was still green, but the seeds were large and yielded 

 a milky juice on being compressed. The third sample was taken 

 when the straw was turning yellow and the seeds were full of starch, 

 though still green and very soft. The fourth sample was obtained 

 when the straw was yellow and rather dry and the seeds were hard 

 and no longer juicy, but yellow ripe. The fifth sample was taken 

 when both straw and grain were dry and the latter easily shaken 

 out of the ears. About one hundred seeds of each sample were 

 sown in good soil in earthenware jars. The percentage of germi- 

 nation is shown in the following tabular statement : 



Hellriegel says that the young plants from the overripe seeds 

 were decidedly the strongest and most vigorous, the others being 

 smaller and feebler very much in proportion as the seeds from 

 which they grew had been gathered earlier. 



Condition of the Parent Plant. Sickly looking plants develop 

 poor seed, and such seed produce feeble plants. It may be some- 

 what troublesome to go over a field of grain and select seed by 



