628 EXPERIMENT STATION RECORD. 



rapid growth moves basipetally over leaf and sheath, then down over the 

 internode, the root ring at the base of an internode showing a development of 

 its own which is apparently independent of that of the other parts. 



It is thought that these studies may be used to throw light on the origin of 

 the disease called top rot in Java (the cause of which is thought to be unfavor- 

 able conditions of growth) by indicating the time at which this trouble begins 

 to affect the growth of the cane. 



Stomatal structure in sugar cane, J. Kuypee {Arch. SuUcerindus. Ncder- 

 land. Indie, 22 (1914), No. 47, pp. 1679-1690, pJs. 2, fig. i).— Summarizing a 

 .study of the structures and relations observed in the stomatal region in sugar 

 cane, the author claims that while any very considerable opening of the central 

 slit is prevented by the thickness of the cell walls, the whole guard cell can move a 

 little on account of its hinge-like attachment to the next cell. The varying 

 relations of the accessory cells are also discussed. 



The closure of the stomata was apparently complete after the plant had been 

 kept in darkness for two days. 



The author concludes that the guard cells may vary the stomatal opening in 

 a very small degree by changing their position between the neighboring epi- 

 dermal cells, the position and structure of the accessory cells making it pos- 

 sible to change also the length of the stomatal slit. 



The accessory cells are said to originate in epidermal cells on both sides of 

 the mother cells which give rise to the guard cells. Particulars are given re- 

 garding the contents of both guard and accessory cells. 



The influence of temperature on phototropism, Marie S. De Vries (Rcc. 

 Trav. Bot. N^erland., 11 (1914), No. 3, pp. 195-290. figs. 7).— Details and results 

 are given of an extended series of experiments testing the relations of prewarm- 

 ing (as regards degree and exposure period), light intensity, and readiness of 

 phototropic response in coleoptiles of Arena sotira. 



Response proved to be independent of the duration of prewarming between 

 and 25° C. From 27.5 to 30° the amount of light required for a given 

 response was decreased by lengthening the period of prewarming. At and 

 above 32.5°, the longer periods of prewarming exerted an unfavorable influence 

 on perception, as shown by the increased light requirement for a given reaction. 

 The effects of prewarming, favorable or unfavorable, decreased rapidly after 

 the early stages until they became constant. The reaction period also showed 

 considerable dependence upon temperature. 



The physiology of pollination, Y. Tokugawa (Jour. Col. Sci., Imp. Univ. 

 Tokyo, So (191.',), Art. 8. pp. 5.?. figs. 2). — The author has made a study of 

 pollen development in connection with ovarial structure and media as related 

 to the possibility of hybridization in nature. 



It is stated that the pollen tube requires for its successful development a 

 certain degree of moisture and osmotic pressure, besides, in some cases at least, 

 a special stimulus. Pollen grains are affected unfavorably in different degrees 

 by inorganic salts, those of the heavy metals being in general the most injurious. 

 The life period of the grains is greatly affected by variations in moisture. 

 Sugar and nitrogenous material given together favor pollen development, 

 different species showing high degrees of specilicity in this respect. The pollen 

 tubes pass readily into agar or gelatin. 



The pollen tube exliibits chemotropisra toward the pistillate opening and the 

 raicropylo, but its progress within the canal is thought to be mechanical. 



Between monocotyledonous and dicotyledonous plants there can be a pene- 

 tration of the pistillate opening and a certain amount of growth by the pollen 

 tube. The ovary, however, is not reached, probably on account of the lack of 



