746 EXPERIMENT STATION RECORD. 



3910 with a new sulphur emulsion known as " Sulfabion " in combating the 

 grape Oidium gave negative results. 



Diseases of the pineapple, L. D. Larsen {Hawaiimi Sugar Planters' 8ta., 

 Path, and Physiol. Bui. 10, pp. 9-70, figs. 26). — Descriptions are given of the 

 common diseases of the pineapple which occur in Hawaii, together with the 

 results of experiments on several of the more injurious, descriptions of the 

 causative organisms, and methods of control. 



The author claims that the most prevalent and destructive parasite con- 

 nected with the pathology of pineapples is TMelaviopsis paradoxa {T. etha- 

 ceticus). In a general study of this fungus it was found that sunlight was very 

 destructive to both its mycelium and spores. An exposure of 24 hours during 

 the summer to the direct sunlight destroyed both the spores and mycelium, but 

 during the fall and winter the results were less pronounced. Successful cross- 

 inoculations were made with pure cultures of the sugar cane and pineapple 

 Thielaviopsis on both sugar cane and pineapples, thus proving the identity of 

 these organisms. 



In a study of diseased pineapple tissues, 4 organisms were reiieatedly found, 

 viz, T. paradoxa, Fusarium' sp., Eurotium sp., and a yeast-like organism desig- 

 nated as Culture No. 26. Inoculation experiments wnth pure cultures of these 

 4 organisms showed that T. paradoxa was the cause of 3 distinct pineapple dis- 

 eases, viz, a soft rot of the fruit, a base rot of the crown, and a leaf spot in 

 which the infection occurs through wounds. The Fusarium produced a brown 

 rot which occurs usually on the ripening fruit, while the yeast-like organism 

 26 probably causes a ripe rot which is always characterized by the odor of 

 alcoholic fermentation. It was found that the Thielaviopsis fungus was 

 capable of infecting perfectly sound, unbruised pineapples, provided moist 

 atmospheric conditions prevailed, and that it attacked green pineapples quite 

 as readily as ripe ones. In the base rot of the crown, the newly planted cut- 

 tings are attacked just at the ground by the fungus, producing a soft rot which 

 often kills the affected plant. 



In addition to the above described diseases, the author discusses sun scald, 

 wilt (the cause of which is as yet unknown), tangleroot, nematode root galls, 

 and manganese yellows (E. S. R., 21, p. 139), all of which occur in Hawaii, 

 and spike, sanding, and heart rot or bitter heart, which have not yet been 

 found on the islands. 



A study on gummosis of Pmnus and Citrus, with observations on squa- 

 mosis and exanthema of the Citrus, O. Butler {Ann. Bot. [London], 25 

 {1911), No. 97, pp. 107-153, j}ls. //, figs. 3). — The author reports the results of 

 investigations on the nature and cause of gummosis, in which the histoi'y and 

 description of the disease, the chemistry of the gums, and the histology, cause, 

 nature, and preventive and remedial measures for gummosis are discussed. 



As a result of these investigations the author claims that the gummosis of 

 Prunus and Citrus are indistinguishable diseases and identical in histological 

 development and causal relationships. The disease is claimed to be due to 

 hydrolysis of the walls of the embryonic wood cells which develop into a sus- 

 ceptible tissue. The dissolution of the cell walls begins in the secondary lamella 

 and almost coincidently in the primary membrane, while the dissolution of the 

 third lamella proceeds centripetally. With its final destruction the cell con- 

 tents become a part of the gum mass. The cell contents are not actively con- 

 cerned, nor does starch play any role whatever in gum formation. Gummosis 

 develops autogenously, and is induced by all manner of traumatisms, provided 

 they act as growth stimulants to the cambium. Once incited, the simultaneous 

 concurrence of two conditions, one physiological and the other environmental, is 

 necessary for the development of the disease. The cambium must be actively 



