GRASSES, CLOVER, AND ALFALFA 215 



tions induced the formation of a large percentage of infertile 

 ovules. All the cells remained sporophytic, no reduction taking 

 place with the formation of an embryo sac. As much as 100 

 per cent, ovule infertility was found in the first clover crop. 

 The rate of pollen tube growth was shown to be much slower in 

 self- than in cross-pollinated plants. It is probable that pollen- 

 tube growth is too slow to effect fertilization when the plant is 

 selfed. The pollen of red clover is easily burst by an excess 

 supply of moisture. Martin (1913) demonstrated that good 

 artificial germination of pollen could be obtained on membranes 

 which were just moist enough properly to regulate the supply of 

 water to the pollen. He suggests that the stigma of red clover 

 performs the same function as the membranes. 



The above facts necessitate a method of breeding which 

 is essentially a restricted form of mass selection. Before starting 

 selection it is desirable to make comparisons of the varieties prod- 

 uced by other breeders and of commercial seed from different 

 sources to obtain the best form for further breeding operations. 

 A seed plot may then be used, in which each plant is spaced 

 so that its characters may be determined. Undesirable plants 

 should be removed before pollination. By repeating this process, 

 forms with the desired characteristics and with practical uni- 

 formity may be isolated. 



Selection for Disease -Resistant Clover. Clover anthracnose 

 (Colletotrichum trifolii), causes serious injury to red clover in 

 certain regions. Bain and Essary (1906) issued a preliminary 

 report on isolating an anthracnose resistant red clover. Healthy 

 plants in a badly infested field were located late in the season 

 after most plants had been killed by the disease. The seeds of 

 the chosen plants were planted separately in alternate rows with 

 ordinary commercial seed. Measures were taken to insure the 

 infection of every seedling with anthracnose. By June 1 the 

 commercial plants began to show symptoms of the disease and 

 by the middle of September not more than 5 per cent, of them 

 were living, while 95 per cent, of the selections were healthy 

 and making a fair average growth. Some of the latter showed 

 small lesions, but growth was not seriously injured. 



ALFALFA 



Alfalfa is one of the oldest, if not the oldest, plant cultivated 

 for its forage only (Piper, 1916). Most of the cultivated forms 



