CURRENT LITERATURE 



NOTES FOR STUDENTS 



Weather and fruitfulness. — Dorsey 1 has done much to place on an 

 experimental basis a subject concerning which there have been many errone- 

 ous popular beliefs. In so far as it affects pollination and fertilization, he 

 divides weather into 4 components, rain, temperature, wind, and sunshine. 

 Wind and sunshine in themselves are of minor importance. Rain prevents 

 the dehiscence of the anthers, or causes them to close if they have already 

 dehisced. While this is beneficial in retaining much of the pollen in the 

 anther during a rain, the pollen is not available for pollination during this 

 time. Contrary to popular belief, rain does not cause the pollen to burst, 

 and although the stigmatic fluid may be diluted thereby, this does not seem 

 to be injurious. Some pollen may be washed from the stigma by rain, but an 

 abundance is left for fertilization. Rain does not injure the viability of pollen. 

 Low temperatures retard the growth of the pollen tube, but do not seem to 

 cause delay in the abscission of the style. The stigma is receptive for 4-6 days 

 and then rapidly disintegrates. The style ' abscisses 8-12 days after bloom. 

 A delay in pollination due to rain, or slow pollen tube growth due to low tem- 

 peratures, may therefore eliminate fertilization by preventing the pollen tube 

 from passing the point of abscission before the abscission of the style. Apply- 

 ing this analysis of weather to certain years of fruitfulness and to certain other 

 years of non-fruitfulness, it is found that each year there is a definite 

 correlation between the weather and the setting of fruit. The experiments 

 are thus given a practical test. — S. V. Eaton. 



Determination of biological fluids. — Duggar and Dodge, 2 after dis- 

 cussing some of the difficulties encountered in examining biological fluids, 

 particularly colored plant juices, by the indicator method of H ion determina- 

 tion, describe a new method which they have found satisfactory for the exami- 

 nation of colored plant juices. "The method consisted in simply arranging for 

 each side of the colorimeter a pair of cups slipping to a certain depth one into 

 the other. The method of procedure is then as follows. For the lefthand 



1 Dorsey, If, J., Relation of weather to fruitfulness in the plum. Jour. Agric. 

 Res. 17:103-126. pis. 13-15. fig. r. 1919. 



2 Duggar, B. M., and Dodge, C. W., The use of the colorimeter in the indicator 

 method of H ion determination with biological fluids. Ann. Mo. Bot. Gard. 6:61-70. 

 1919. 



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