CHAPTER VII 



SEEDING, PLANTING AND YIELDS 



lELD CROPS ARE PROPAGATED chiefly by means of seeds, rather than by means 

 of cuttings or other special parts. Moreover, the seed-propagation is of the 

 easiest and simplest kind, adaptable to wholesale methods. There is no necessity 

 for the employing of grafting or other very special practices. For these reasons, 

 the subject of propagation of plants is usually considered to belong to that phase of 

 agriculture known as horticulture. 



A very few of the field crops are propagated by asexual parts or cuttings of them, 

 as white potato, sweet-potato, sugar-cane, cassava, chicory. Whenever cutting- 

 propagated plants are raised from seeds, the seedlings are likely to vary greatly, so 



greatly, in fact, that seed propagation may be employed with such plants for the purpose of securing 



new varieties. The white or Irish potato is a good 



example ; and as this species seeds relatively freely 



and seedlings are easily grown, the number of varie- 

 ties is very large. The sweet-potato and sugar-cane 



seed so rarely, at least in this country, that this 



means of securing new varieties is practically little 



employed, and reliance must be had on variation 



through asexual parts. The reason why seeds give 



such uncertain results in cutting-propagated plants, 



as potatoes, apples, grapes, strawberries, is because 



there has been no seed-selection to make them "come 



true." In the seed-propagated plants, as the cereal 



grains and garden vegetables, selection has been 



practiced so long and so carefully that the tendency to vary has been largely bred out. The tendency 



of seeds to give variable offspring is greatly increased, as a general thing, by crossing, whereby 



different elements or tendencies are combined. 



Fig. 189. Seed storage room. 



Quality m seeds. 



The merits of good agricultural seeds lie in the following characteristics : 



They are " strong," or able to produce vigorous normal plants ; 



They are free of disease ; 



They are of the proper variety or strain ; 



The sample carries no impurities or adulterations. 



Whether seeds are strong depends in part on the vigor or strength of the plants that produced 

 them, in part on their age, in part on the way in which they were grown, and in part on the way in 

 which they have been handled and kept. Tables of longevity, — that is, of the number of years that 



seeds retain their germinating power, — are of some 

 value in determining whether seeds of a given age 

 are likely to be good. Such a table, compiled from 

 various sources, for some of the field crops is given 

 below. Such tables present only averages, however, 

 and are likely to be of more use as information than 

 as advice. Many conditions infiuence the longevity 

 of a seed. When well ripened and kept in a dry cool 

 aerated storehouse, the viability may be retained 

 longer for some seeds than the figures indicate. The 



Fig. J90. Poor and good cabinets. In the ehest on the 

 left> rats and mice pa.ss readily from one drawer to the 

 other. In the one on the right, this is impossible be- 

 cause of solid partition between drawers. (Oornell 

 Reading-Course Bulletin,) 



(131) 



