RED-CLOVER. SEED PRODUCTION. 9 
100 per cent of infertile ovules. With such plants the presence of 
bees is not a matter of importance, for the ovules have no reproduc- 
tive cells; hence there can be no fertilization and no production of 
seed. During the second crop, when the season is generally dry and 
favorable for seed setting, there is some infertility, ranging from a 
low percentage or none in some plants to a high percentage in others. 
It is very probable that this infertility of ovules is to a greater or less 
degree a hereditary character and that the production of a high- 
yielding strain will consist, among other features, in selecting those 
plants with the least erdente toward infertility. 
POLLEN OF RED CLOVER. 
The pollen grains of red clover are almost globular when turgid, 
with a little flattening at the germ pores. When measured in a 
25 per cent cane-sugar solution the pollen grains have an average 
size of 44.5 by 43 u (fig. 2, #). The grains are not fully turgid when 
shed from the anthers and one diameter in each is shortened and 
the other diameter lengthened by an infolding of the wall. In this 
condition Martin (25) found the average dimensions of 100 pollen 
orains to be 26 by 48 yw, while Miss Clark (30) found the average size | 
of 1,024 pollen grains to be 31.7 by 56.29 pz. : 
_ When dropped in water the pollen grains take it up very rapidly 
and burst almost instantly. On account of this feature of the pollen 
there can be little effective pollination when the flowers are wet. 
Pellination at night or in the morning when the flowers are wet 
with dew is not likely to be effective. 
Germination of the pollen of red clover was found by Martin (25) 
to depend upon a proper water supply. Good artificial germination 
can be secured on parchment paper or animal membranes which are 
just moist enough to permit the pollen to absorb the requisite amount 
of water for germination. Germination takes place within a limited 
range of variation in the water supply, and it is only by trials of 
wetting and drying that the proper moisture content of the mem- 
branes may be secured. Under proper conditions of moisture and 
temperature, germination takes place usually in 8 to 10 minutes. 
FUNCTION OF THE STIGMAS OF RED-CLOVER FLOWERS. 
Microchemical tests of the stigmas of red-clover flowers show 
no sugars or starches present. An oily emulsion, however, does 
occur in the papille. Crushed stigmas placed on animal membranes 
had no apparent effect on the See of the pollen or on the 
directions of the tubes. 
When pollen is deposited on the stigmas it lodges between the 
papille, takes up water, and soon tenes turgid, but the water 
supply is so regulated te the stigmas that no yon ine occurs. It 
2990°—Bull. 289—15 = : 
