CONTROLLING POLLINATION 71 



All but the outer florets of eight of the central spikelets are removed. 

 The upper and lower spikelets are cut off with shears and the 

 central floret of each remaining spikelet is removed by grasping 

 it near the top with the forceps and giving a downward pull. 

 The forceps are then carefully pushed between the palea and 

 lemma and the flower opened. The three stamens are removed 

 in one operation, if possible. Care is taken not to pinch the 

 anthers too tightly and break them open. Spikes are used in 

 which the anthers are just beginning to turn yellow. Anthers 

 from the variety to be used as the pollen parent are removed from 

 the florets. Experience has shown that it is best to use only 

 anthers which are ready to dehisce and which open after being 

 held in the hand or soon after being placed in a watch glass in the 

 sun. A single ripe anther is introduced into each floret. 



Where greenhouse facilities are available, crosses may ad- 

 vantageously be made in the winter or early spring months. 

 This method is used extensively by the Plant Breeding depart- 

 ment of Cornell University. When all conditions are favorable, 

 between 50 and 100 per cent, of crossed seeds may be obtained. 



Barley and oats are handled in nearly the same manner as 

 wheat. With barley it is often necessary to emasculate before 

 the spikes have entirely protruded from the leaf sheath. The 

 work is somewhat more difficult, as the flowering parts are much 

 more tender than in wheat. For this reason forceps and shears 

 with very fine points and thin blades are needed. Apparently 

 under certain environmental conditions (Arlington Farm, Va., 

 Norton, 1902) and likewise at University Farm, Minn., oat 

 flowers nearly all bloom in the late afternoon. Artificial 

 pollination under these conditions is more easily performed in 

 the afternoon from one o'clock until mature pollen is no longer 

 easily collected. 



Among the difficulties of artificial crossing in the field are un- 

 favorable weather conditions. Too much rain or long-continued 

 rains prevent work. Jellneck (1918) compared two methods of 

 crossing wheats: (1) emasculation and pollination by placing a 

 ripe anther in the floret; (2) emasculating spikes as usual and 

 tying these with spikes of similar maturity belonging to the 

 pollen parent and covering with a paper bag. In 1916 method 

 (2) gave twice as great setting of seed as method (1). In 1917 

 conditions were very unfavorable and no seed was produced by 



