DEVELOPMENT OF VARIETIES 89 



standing up straight they turned off at a right angle at or 

 near the point where the ear was produced, thus showing 

 the tassel on a level with the ear. Many of the tassels 

 were very deficient in pollen." In another plot from self- 

 fertilized seed, nearly all the tassels were abortive. All 

 the plants from self-fertilized seed produced a greater pro- 

 portion of barren stalks or poorly filled ears than plants of 

 the same varieties from hand-crossed seed or from seed 

 naturally fertilized. On the other hand, the flowers of 

 barley and wheat are so constructed that their flowers 

 seldom open and hence are naturally self-fertilized, but 

 even here artificial crossing results in increased produc- 

 tiveness. 



The effect of cross-pollination is not always apparent 

 in the progeny of the first generation, but is frequently 

 plainly to be seen in the crossed fruit or seed the first year. 

 Differences may appear, however, as the result of the cross 

 the second or later generation, which were not suspected. 

 When corn is crossed it is generally believed that the effect 

 of the cross is apparent the first year in the grain, but 

 careful experiments plainly show that this is not so, and 

 that flint corn grains which do not show a trace of the 

 admixture of sweet corn the first generation may produce 

 ears the second generation showing some of the character- 

 istics of the sweet corn, and the same is true of other kinds 

 that are crossed. The same truth undoubtedly holds good 

 in the case of other plants. 



Mixing Varieties. Practically varieties of plants can be 

 mixed only in the blossom ; and in order to mix the different 

 varieties both must be in blossom at the same time. On 

 this account potatoes do not mix in the hill. The varieties 

 of some species of plants are much inclined to mix. Any 

 two varieties of corn, melons, squashes, and cucumbers are 



