46 EXPERIMENT STATION RECORD. 



which point is probably of valuf in indicatinj; llic Irrcs wliich should be pre- 

 served in the i)ernianent plantation. 



[Pot experiments with fertilizers for rubber), Ai.uk K. Tiiomp.son (Hdiniii 

 Sta. Rpt. 1908, pp. 6'2-6V/). — A fertilizer experiment was made with r\ibber 

 plants, the wire-basket method devised by the liureau of Soils of this Dejjart- 

 ment beinjj used. 



The results for Para rubber show that where manure, sodium nitrate, or 

 lime was the single fertilizer, transpiration increased materially. Combinations 

 of acid phosphate and potassium sulphate gave a large increase, but acid phos- 

 phate in other combinations either decreased the transpiration or gave but 

 little increase. 



In the work with Ceara rubber the best results were obtained with lime, 

 sodium nitrate, and the two combinations, sodium nitrate and potassium sul- 

 phate, and sodium nitrate, potassium sulphate, and acid phosphate. Manure 

 alone and potassium sulphate alone gave fair results. The experiments as a 

 whole indicate that sodium nitrate used alone is a good fertilizer for rubber 

 trees, while acid phosphate appears to have some deleterious effect ui)on them. 



Caoutchouc and gutta-percha in the Dutch East Indies (lier. Handel u. 

 Indus., 13 (1009), No. -'/, pp. 137-1 -'/l'). — A consular report on the rubber in- 

 dustry in the Dutcli East Indies, relative to its extent, varieties grown, ex- 

 ploitation, and commerce. 



Ecanda rubber (Raphionacme utilis) (Roy. Bot. Gard. Krw, Bui. Misc. 

 Inform., 1909, No. 8, pp. 321-325, pi. 1, figs. 3).— This is a further report on this 

 recently discovered tuberous rubber plant (E. S. R., 20, p. 545), relative to its 

 mode of growth under natural conditions and its exploitation in Angola, together 

 with notes on the growth of seedlings being studied at the Kew gardens. 



DISEASES OF PLANTS. 



The development of disease-resistant plants, G. M. Reed (Ann. Rpt. Mo. 

 Bd. Hort., 2 {1908), pp. 28Jf-296). — A summary is given of various investigations 

 that have been carried on as to the prevention of plant diseases by the develop- 

 ment of disease resistance on the part of the host. A considerable number of 

 instances are quoted in which some degree of resistance has been attained, either 

 by selection of plants that have withstood attack or by crossbreeding varieties 

 known to be resistant with susceptible ones and selecting the resistant progeny. 



Some plant bacterial diseases, W. G. Sackktt i Houtliircsl. fitocknuDi, 28 

 (J909), No. 15, pp. 1, 4, 5). — An account is given of a bacterial disease of alfalfa 

 and of pear blight. 



The alfalfa disease has been previously reported (B. S. R., 18, p. 553), and 

 further investigations have confirmed the conclusion that it is of bacterial 

 origin. Its presence can be recognized, it is said, by the short sickly growth 

 of the first crop and the absence of the deep green color characteristic of a 

 thrifty stand. A close examination of the stems show them to be shriveled 

 and blackened for 2 or 3 in. from the ground, the infection attacking the 

 plants next to the soil and working up the stem. As the disease progresses it 

 produces a watery, semitran spa rent, brownish appearance of the tissues, which 

 turn black with age. The leaves attached to the diseased part of the stem 

 usually show the watery yellow color at the base and especially at the base of 

 the petioles. One-year-old plants exhibit blackened areas in the crown and 

 black streaks running down into the tap root. As the plant grows older the 

 blackening increases until the whole crown is involved, and either the crown 

 buds are destroyed or the root is no longer able to perform its functions. 



