FIELD CROPS. 833 



had been cross-pollinated for 55 hours showed that fertilization had taken 

 place in all of them." 



The use of the thumb and finjier or of a toothpick or toothbrush in artificial 

 manipulation of the flower resulted in practically no seed in covered heads 

 and in a reduced number in exposed heads as compared with those not covered 

 and not manipulated. 



As results of covering untreated heads of clover with tarlatan it is noted that 

 " since no more seed was produced by these heads than may be accounted for by 

 insects working on the flowers when they were occasionally exposed for a short 

 time on account of rains or grasshoppers, we may say that clover flowers must 

 be pollinated by some agency before any seed is produced." 



Clover heads covered before any flowers opened and kept covered, except 

 while being artificially self-pollinated, until mature produced an average of 0.16 

 seed per head in 1911 and 0.09 in 1912. One hundred and twenty-five heads 

 were worked in the first instance and 170 in the second. Not a single seed was 

 produced in flowers pollinated with pollen from another head on the same pri- 

 mary branch, and only one seed was produced in using pollen from a head on a 

 different primary branch of the same plant when 200 flowers were used on 10 

 heads. Fourteen and three-tenths seeds per head were produced in 13 heads, in 

 which 20 flowers each were pollinated from a separate plant. " The results 

 obtained in the last three experiments, as well as with all preceding ones, show 

 that clover is practically self-sterile and that pollen must come from a separate 

 plant in order to efl:ect fertilization." 



" The bumblebee is an efficient cross-pollinator of red clover. Bumblebees are 

 able to pollinate from 30 to 35 flowers a minute. The honeybee proved to be as 

 eflicient a cross-pollinator of red clover as the bumblebee in 1911. When the 

 precipitation was considerably below normal in June, July, and August, 1911, 

 and but few nectar-producing plants were to be found, honeybees collected large 

 quantities of pollen from red clover. In order to collect pollen they must spring 

 the keels of the flowers. In doing this they cross-pollinate the flowers. 



"A clover cross-pollinizing machine which was offered for sale on the market 

 did not prove to be an efficient cross-pollinator of red clover. The various types 

 of hand-operated brushes which were used did not prove efficient as cross-polli- 

 nators of red clover. In nearly all cases where these brushes were used the seed 

 yield was decreased instead of increased. This was imdoubtedly due to the 

 bristles of the brushes injuring the flowers, since the average seed yield of the 

 plats which received these treatments with the brushes was lower than that of 

 the plats which received but one treatment." 



A bibliography of nearly 50 titles Is appended. 



Custom ginning as a factor in cotton-seed deterioration, D. A. Saunders 

 and P. V. Caedon {U. S. Dept. Agr. Bui. 288 (1915), pp. 8, figs. 5).— This 

 bulletin gives the results of a test at Greenville, Tex., to determine the amount 

 of mixing of cotton seed that may occur at the gin. The amounts of red seeds 

 that appeared in samples of seeds taken at 5, 10, 15, 20, 25, and 30 minutes after 

 the starting of the gin, in which the seed roll in the roll box had been stained 

 red, were 52 per cent, 17.1, 7.4, 2.8, 0.5, and 0.1, respectively. 



" It has been shown that no less than 14 to 16 per cent, and probably much 

 more, of the seed delivered to a patron at custom gins as ordinarily operated is 

 seed of the variety ginned just previous to the arrival of his cotton. The results 

 indicate also that some seeds from the second bale preceding are likely to 

 appear in the seed delivered to the patron. This means that if different varie- 

 ties are being ginned consecutively a patron will receive in the seed delivered to 

 him at the gin an admixture of at least three varieties. It is apparent that if 



