542 EXPERIMENT STATION RECORD. [Vol.41 



studying the structure of laticiferous vessels of Hevea, and to ascertain some 

 linowledge about the cytologj' of this tree in connection with the physiological 

 signification of latex. 



The author found that in the laticiferous vessels of Hevea both protoplasm 

 and nuclei occur, but the nuclei are larger than those of other cortex cells. 

 The nuclei are placed in protoplasm where also occur vacuoles. It is con- 

 cluded that the latex of Hevea is cell sap, which generally occurs in the 

 vacuoles of the laticiferous vessels. Frequently many of the nuclei of the 

 laticiferous vessels unite in one spot, and they have also been observed to pass 

 from one vessel to another through the wall openings. 



Variability in plantation rubber, C. de Vries and W. Spoon (Arch. Rubber- 

 cult. Nederland. Indie, 3 (1919), No. 6, pp. 2//6-276).— Results are given of an- 

 alyses conducted at the Central Rubber Station, showing the variation in 

 rubber samples collected from a number of estates in the Netherlands Indies. 



The relation between the specific gravity of latex and serum and the 

 rubber content of latex, C. de Veies {Arch. Rubbercult. Nederland. Indie, 3 

 {1919), No. 5, pp. 183-206, figs. 2). — Results are given of experiments conducted 

 with pure undiluted latex collected from trees under different conditions, such 

 as continued tapping after a period of rest, light or heavy tapping systems, 

 from trees before and after pollarding, from trees given different periods of 

 rest and shallow tapping, and from individual trees. 



The tests as a whole show that there is a very close relation between the 

 specific gravity and the rubber content of original latex. For the specific 

 gravity of original serum varying values are to be expected, depending upon 

 the composition of the serum owing to physiological factors, but these varia- 

 tions are within a limited range. Whether the specific gravity of rubber in 

 latex is constant or varies somewhat because of absorption phenomena or 

 changes in the composition of the caoutchouc hydrocarbon remains to be inves- 

 tigated. The rubber content of the original latex is lowered by all factors 

 which put a heavy stress on the trees. 



Tapping experiments on Hevea brasiliensis, A. W. K. de Jong (Arch. Rub- 

 bercult. Nederland. Indie, 3 {1919), No. 6, pp. 277, 278). — This paper summarizes 

 the results of experiments in which tapping was conducted on a quarter, a 

 third, and a half of the circumference of the tree with one left-hand cut. The 

 experiment was conducted on three different tapping areas. Averaging the 

 results of the three areas, the riabber yield increased from 100 : 114 : 122 as the 

 cut was increased from one-fourth to one-half of the circumference. 



The application of preservatives to renewing bark of rubber, T. Fetch 

 {Dept, Agr. Ceylon Leaflet 9 {1918), pp. 4)- — This leaflet summarizes in very 

 condensed form considerable information obtained in experiments to determine 

 what amount of injury would be caused to renewing bark of Hevea by the 

 application of preservatives, a number of which were tested in these 

 experiments. 



DISEASES OF PLANTS. 



Report of associate plant pathologist, C. D. Sherbakoff {Florida F>ta. Rpt. 

 1918, pp. 68-78, figs. .) ) . — The author gives a report on investigations of several 

 diseases of truck crops, among them being a rot of eggplants due to Phomopsis 

 rexans, bacterial blight or rot of solanaceous plants, buckeye rot of tomatoes, 

 and damping-off of celery. 



In the eggplant seed tests, studies were carried on to determine the proba- 

 bility of the seed carrying infection. The results showed that the introduction 

 of the Phoniopsis into the seed bed took place by means of seed which had 

 been contaminated with the fungus. It is thought that the fungus is not a 



