AGEICULTURAL BOTANY. 527 



the pollen, descriptions are given of germination experiments in which the 

 intluence of a number of factors, such as temperature, moisture, etc., are given. 



The germination and subse(]uent growth of the pollen tube are said to be 

 very similar to the germination and growth of ordinary spores. Most pollen 

 grains were found to germinate in solutions of cane sugar, although in the 

 experiments reported the pollen of the tomato germinated best in a slightly 

 acidulated sugar solution and the pollen of Phaseolus multiflorus in pure olive 

 oil. A considerable range of concentration of solutions was noted for some 

 species, while for others the range of concentration was quite restricted. 



The growth of the pollen tube and the movement down the style was investi- 

 gated, and the author believes that the length of the pollen tube of a given 

 species is often a barrier against the cross pollination of related species and 

 varieties. 



In the experiments on temperature influence, pollen in a dry atmosphere was 

 not seriously affected by temperatures of 25 to 55° C, but below 25° the ger- 

 mination was interfered with. A temperature of TO to 80° in a saturated 

 atmosphere was found fatal to the pollen of the peach, apple, and plum, and the 

 author states that the pollen of these trees often burst in great masses during 

 warm spring rains. Freezing temperatures. — 1.5 to — 1°, were not seriously 

 injurious to the pollen of the apple, pear, or plum, but destroyed nearly half 

 the i)each and apricot pollen. The pistils of the varieties experimented upon 

 were found more susceptible to the low temperature than was pollen. 



Sunshine was found to have little or no effect on the germination of pollen 

 or on the growth of the pollen tube in most plants. The germination and 

 growth of pollen of the tomato were found to be decidedly retarded by cloudy 

 weather, and the anthers of the tomato required a certain amount of sunshine 

 f(»r the proper development of their jtollen. This was also true in several si)ecies 

 of Lilium. 



The lack of culture and fertility in orchards was found to reduce the pro- 

 duction and fertility of pollen. 



Experiments on the longevity of apple, pear, and plum pollen showed that 

 in a dry place at temperatures ranging from 7 to 2G° it could be kept for a 

 considerable time, apple pollen retaining its vitality for 6 months or longer. 

 With proper precautions it is possible that pollen may safely be shipped from 

 one pait of the country to another without losing its viability or fertility. 



Under favorable conditions it is found to require from 9 to 82 hours for the 

 jtoUen tube of apitles. ])lums, and cherries to reach the ovary after having been 

 placed on the stigma. This would indicate that the length of time required 

 for the fertilization is less than is commonly believed, 2 or 3 bright warm days 

 at the time of full bloom being sufficient for the setting of the fruit. The 

 stigmas of apples were found to be receptive for from 4 to 6 days, whether pol- 

 linated or not. Continuous rainy weather for 6 or more days would probably 

 result in a total failure of the crop in case of most fruits. 



Summarizing the i-esults, the author states that the factors which affect the 

 fertility and production of pollen over which the orchardist has control are site, 

 soil, planting, cultivation, pruning, spi-aying, and selection of suitable varieties. 

 Those over which there is little or no control are freezing temperatures, con- 

 tinuous rainfall during the flowering period, high temperature with a large 

 amount of moisture at the time of flowering, and the absence of insects and 

 wind to transfer the pollen. 



Handbook of flower pollination, P. Knuth, trans, by J. R. A. Davis (Oopfonl, 

 J!l()!l, vol. 3, pp. IV+G.'i'i. fl'!/s. ;>(>,S). — This is the third and concluding volume 

 of the work previously noted ( E. S. II., 20. p. 326). It is based on H. Miiller's 

 work on the Fertilization of Flowers by Insects, and gives the results of 



