DI8EA8E8 OF PLANTS. 981 



brought out in some data in which it is shows that 40 tapped trees, averaging 2 ft. 

 .Sin. in girth per tree, produced L8.4 lbs. of rubber, while 20 trees averaging t ft. 2 

 in. in girth yielded 25.4 lbs. of rubber. In another instance 50 trees averaging L.75 

 ft. in girth yielded L8.5 lbs. of rubber, while only 15 tree.-, 5.6 ft. in girth, yielded 

 33.5 lbs. of rubber. 



Extensive tables are given showing the yield of rubber from morning and evening 

 tappings and by different methods of tapping, and growth of different trees under 

 observation. Morning tappings have produced more rubber than evening tappings. 



Note on the germination of teak and other seed, IJ. S. Pearson | Indian 

 Forester, 81 (1905), No. 11, pp. 685-688). — The germination of teak seed wasseriouslj 

 injured byabnormallj heavy falls of rain. Dhawraseed i Anogeissus latifolia), which 

 the author heretofore has been unable to make germinate, was successfully germi- 

 nated by Bowing the seed on well irrigated raised beds, the soil being mixed with a 

 large quantity of coarse saml, the seed sown in June and daily watered by hand. 

 The germination was greatly facilitated by covering the bed with a thick layer of 

 leaves and branches about is in. above the ground. 



The teak timber trade of Burma, T. A. II luxwell I Indian Forester, 81 

 No. 11, pp. 618-685).- The teak timber trade of Burma is shown to be steadily 

 decreasing, while that of Siam is gradually increasing. The causes of this decrease 

 arc discussed, chief of which arc the diminution in the supply of old girdled timber 

 of large size in Burma, less accessible areas, the increase in the cost of elephants nec- 

 essary for the work, more rigid requirements as regards working, and increased rate 

 of royalty demanded. Tables are given showing the total output of teak in Burma 

 for the years 1887 to 1904, and of exports of teak from Burma and Siam during 

 approximately the same period. 



DISEASES OF PLANTS. 



The physiology of diseased plants, L. Montemabttot (A/fi 1st. Bat. Univ. 

 /'aria, e. ser., 9 (1904), pp. 63; abs. in Bot. Centbl, 98 (1905), No. //, pp. 276, 277).— 

 A study was made of the respiration, assimilation, transpiration, increase in dry mat- 

 ter, ash, etc., in a number of plants that had been attacked by various plant and 

 animal parasites. Among the plants investigated were grapes, violets, clematis, 

 various grasses, roses, quince, euonymus, etc., the fungi being rusts, mildews, and 

 leaf spots, and the insect attacks being due to mites. 



The different parasites studied are said to be able to exert a stimulative effect on 

 the development of their host plants. This is manifest more in the increased respi- 

 ration than in chlorophyll assimilation, the latter being depressed as respiration is 

 increased. In general the Uredinese excite a greater chlorophyll assimilation on the 

 part of the host. Transpiration was found uniformly greater in diseased than in 

 sound plants, with the exception of euonymus attacked by Chionaspis euonymi. The 

 transpiration under the action of light is increased for a time, after which it markedly 

 diminishes. It also increases w hen ever assimilation is stimulated. Most of the para- 

 sites studied did not seem to have any direct influence on the water or ash content 

 of their hosts, and whatever increase was found was attributed indirectly to the 

 stimulated physiological activity of the plant. 



Attention is called to the fact that many poisons exert stimulating effects on plants 

 when dilute, although they are destructive when used in greater proportions. From 



this the author deduces the hypothesis that the parasites may secrete some poisonous 



Bubstances, possibly zymases or oxydases, which at first have a stimulating effect on 

 the host plant and which disappear with the progress of the disease. 



Plant diseases of Belgium, II. Vanderyst {Bui. Agr. [Brussels'], 91 {1906) i 

 Nos. /', pp. 588-639, figs. I .'; 5, pp. 878-908, figs. 7).— After a general account of the 



Ustilaginea?, in which their common host plants are enumerated, the life cycle of 



