468 EXPERIMENT STATION RECORD. 



ing a bacterium whieli liquifieH gelatine and which, when sown on sterile specimens 

 of living turnips, i)ro(luced the characteristic white rot. Pure cultures of the bac- 

 terium sown upon plants growing in the garden gave identical results. The charac- 

 teristics of the organism, to which he has given the name Psevdomonas destructans, 

 are described. 



The organisju can live for many generations as a saprophyte without losing its 

 virulence as a parasite. In 1898 the author isolated and passed the organism through 

 several cultivations, and in August, 1899, sound turnips were inoculated with the old 

 cultures ami in 5 days the rot was found to have penetrated deeply into the tissues 

 with all the distinctive characteristics of the white rot. 



In order to ascertain the action of the bacterium and to determine wdiether it pro- 

 duced any ferment capable of acting upon the cell wall, cultures were precipitated 

 with alcohol, filtered and digested with distilled water, after which the solution was 

 passed through a Pasteur-Chamberland filter. In this manner a clear, pale, straw- 

 colored liquid was obtained free from bacteria. Thin sections of turnips were sub- 

 jected to the action of this liquid, with the result that the middle lamella was attacked 

 and dissolved, proving that the bacterium secretes an enzym which dissolves the 

 middle lamella antl causes the softening and swelling of the cell Mall. The autlior 

 tested the juice expressed from a rotten turnip and ol)tained, on the addition of cal- 

 cium chlorid, a precipitate of calcium oxalate. Cultures were undertaken which 

 showed the presence of oxalic acid as a product of the organism causing this disease. 

 The oxalic acud acts upon the cell, dissolving the calcium pectate which enters largely 

 into the composition of the middle lamella. In this characteristic the action of the 

 bacterium is said to be precisely similar to that of certain parasitic fungi; in both 

 eases the organisms produce oxalic acid which acts as a toxin to the protoplasm and 

 decomposes the calcium pectate, furthering the dissolution of the cells. There is 

 also secreted a cytase which has a destructive action upon the cell wall and intercel- 

 lular substance. 



From numerous observations made in the field, the author concludes that P. destruc- 

 tans is introduced at a wounded surface. Except in cases where the disease has 

 proceedetl to a large extent, the point from which the decay spreads is indicated by 

 a womid in the epidermis and adjacent tissues. This observation is further sup- 

 ported by failures to infect sound roots except by first making a small incision. 

 Wounds caused l)y snails, slugs, and larvte would furnish the bacterium a means of 

 entrance, :ind it is ])r()l)al)le that the attack is made in this way. 



Studies of some shade tree and timber destroying' fungi, G. F. Atkinson 

 {Neir Turk forndl Sla. Bid. 193, pp. 19S-2S5, fiys. 39). — The author gives the results 

 of several years' study on the injuries i)roduced by some of the higher fungi ui)on 

 shade and timl)er trees. A number of the more prominent species are selected and 

 the relation between the fimgus and its host traced. The species described are I'oly- 

 porui^ horealis, occurring on living or dead pines, spruces, and hemlocks; P. sidplmreua, 

 which occurs on the living trees of the apple, walnut, butternut, locust, oak, ash, pine, 

 hemlock, spruce, etc. ; P. igniarius, which occurs on the apple, oak, alder, beech, 

 birch, maple, and other species of broad-leaved trees; P. jiinicoht, which has hitherto 

 been considered as (H)nfined to various conifers, although » the author rei^orts having 

 observed it on the beech, birch, and maple; and Trainetcs (diii'tk, common on spruces 

 and Italsams. The effect of these different fungi, as shown in the wood and timber 

 of the different trees, is described, and the imjHJrtance of i)roi)er ])runing in order to 

 prevent means of entrance of the mycelium is shown. 



The dry-rot fungus (Merulius lacrymans), K. Henrv {Bui. Soc. Sci. Nancy, 

 3. set., 1 {1900), No. 6, pp. 314-2J7). — After describing the botanical character of the 

 fungus, a resume is given of its physiology, conditions for its existence, action on 

 wood, and suggestions for ]>r('venting its attacks. 



A Fusoma disease, C. von Tubritk (ylr/>. A'. (IcsniidhcitsaDitc, liiol. Aht.,f.' {19(11), _ 



