760 EXPERIMENT STATION RECORD, 



control of die-back, but that its benefits were somewhat hidden by a decrease ot 

 of the disease due to natural causes. 



In the investigations on the gumming of citrus trees the author carried on 

 experiments with a large number of chemicals inserted either in small holes 

 bored into the trunk, or imder the bark or placed on the forming buds. An enzyra 

 and 28 different organic and inorganic chemicals were used in the experiment, and 

 of this number 13 induced the formation of gum. Most of these substances are 

 classed as acids, alkalis, or salts of heavy metals. The production of gum was 

 coincident with the injury caused by the chemicals. The most copious produc- 

 tion of gum was caused by copper sulphate and the other salts of heavy metals, 

 and the injury extended from the point of insertion in the bud or stock to the 

 upper branches. The injury caused by the other compounds was confined to the 

 region of insertion, and the amount of giun produced was relatively small. In 

 all cases the gum was the same in character and appearance, being of a clear 

 amber in color and completely soluble in water. A microscopical examination 

 showed that in all cases the gum originated in the live embryonic xylem tissue 

 outside the dead area produced by the chemical. Enlarged gum pockets were 

 produced in the immature branches of the trees inoculated with copper sulphate 

 and mercury bichlorid, and no differences in development, structure, or external 

 appearance could be recognized between these and the pockets formed during 

 the progress of the die-back disease. The author states that through the swell- 

 ing of the gum collected in the gum cycle by the absorption of water, pres.suri^ 

 is developed, and that If the covering tissue is inelastic a break will occur am; 

 the gum exudes. On the other hand, if the tissue is elastic, as in the Immature 

 branches, the covering tissue is raised and large gum pockets are formed in 

 the stem. 



Report of plant pathologist, H. E. Stevens {Florida Sta. Rpt. 1913, pp. 

 LXXII-LXXXVI). — The Investigations reported upon consisted mostly of a 

 study of melanose, stem-end rot, gummosis, and fruit rot of citrus trees. 



Melanose, caused by Phomopsis eitri, which has been previously described 

 (E. S. R., 28, p. 651), is briefly discussed and results of inoculation experiments 

 are given which confirm previous conclusions regarding this dl-sease and also 

 show that It is due to a specific organism and does not result from any soluble 

 toxin in dead twigs. Experiments were conducted to test the effect of fungicides 

 for the control of melanose, lime sulphur, Bordeaux mixture, and ammoulacal 

 copper carbonate solutions being sprayed upon orange trees in pots In the green- 

 house. Lime sulphur seemed to prevent infection completely, but caused more or 

 less injury to the foliage by burning. Bordeaux mixture and ammonlacal solu- 

 tion of copper carbonate gave about the same degree of control, and the injury 

 to the foliage attributed to Bordeaux mixture was practically negligible, while 

 there was some slight burning in one experiment with the ammonlacal solution 

 of copper. An experiment with pruning on the effect of melanose has been 

 begun, but sufficient time has not elapsed to give exact data regarding It. 



Brief accounts are given of the stem-end rot, fruit rot, and scab. 



The Fusariums from cankered cacao bark and Nectria cancri u. sp., A. A. L. 

 RUTGEBS (Ann. Jard. Bot. Buitenzorg, 2. ser., 12 {1913), pi. 1, pp. 59-63, pis. 

 i). — A study was made of 15 apparent strains of Fusarium (six supposedly 

 belonging to F. colorans and nine to F. theohrom(e) on different substrata. Perl- 

 tliecia of one of the latter appeared to belong to the genus Necti-ia, but to coin- 

 cide with no species yet listed. Accordingly this new species, which Is here de- 

 scribed, received the name N. cancH. 



A trunk disease of the lilac, H. von Schbenk {Ann. Missouri Bot. Gard., 

 1 {1914), No. 2, pp. 253-262, pis. 2). — A destructive trunk disease noted during 

 recent years In and around St. Lonis, Mo., Is described. It Is said to be causad 



I 



