BOTANICAL CHARACTERS T05 



bins"; but such a shortage of pollen is not likely to occur CHAP, 

 throughout the whole period of development of the silks. IV- 



If the silk be injured, the proper fertilization of the ovule 

 may be prevented, with consequent reduction in yield of seed. 



77. Pollination. — Unless a pollen-grain reaches the style 

 no seed will be formed (Fig. 43). The maize plant is 

 anemophilous , i.e. wind-pollinated. The pollen is very light 

 and is carried for long distances by the wind ; there is thus 

 danger of cross-pollination if two sorts of maize are planted 

 near to each other — 400 yards is considered a safe distance 

 though some writers recommend half a mile. Because it is so 

 light, and easily carried by a breath of air, very little pollen 

 usually reaches the silks of the same plant which produces 

 it ; it is carried by the least puff of wind to the plants beyond. 

 The writer has observed cases in which the pollen fell directly 

 on to the silks below, on a very still evening ; but such cases 

 appear to be rare in nature ; and as a rule the arrangement 

 of the leaves is such that they partially protect the silks from 

 such a contingency. 



The maize tassel is much visited by bees, which collect 

 the heavy-scented pollen for food lor their young larvae. But 

 the bees do not visit the silks, and are not, therefore, direct 

 agents in pollination, and the amount of pollen produced is so 

 great that the little taken by the bees is not likely to have 

 any effect on the crop of grain. In South Africa at least three 

 sorts of beetle also visit the tassels, to feed on the pollen 

 (see chap. X.), without affecting the yield. 



An experiment was conducted at the Botanical Experiment 

 Station, Pretoria, to determine the receptivity of silks to 

 pollen at different stages of development, with the following 

 result : Application of pollen on the first day of appearance 

 of the silk resulted in the fertilization of only 14 ovules, 

 situate toward the base of the ear. Of the ear pollinated the 

 second day, about half of the ovules were fertilized, the upper 

 part of the ear being bare of grains. The ear pollinated on 

 the third day was three-fourths covered with grain, the 

 extreme butt and the tip having no grains. From this we 

 conclude that if pollen is not available by the third day, the 

 earliest silks to develop may not be fertilized. 



78. Fertilization. — When a pollen grain is caught among 



