DISEASES OF PLANTS. 651 



A felty, mycelial mass appears on the base of the fallen nuts, and gradually 

 spreads over the entire surface. In this mass are imbedded numerous oval 

 sporangia of a Phytophthora. 



Infection experiments with pure cultures of the fungus were successful in 

 producing the disease in healthy nuts, and also in the leaf sheaths, in the male 

 and female flowers, and in the flower stalks. It is claimed that the infection is 

 produced entirely by zoospores formed in the sporangia, and, according to the 

 gardeners throughout the infected area of Mysore, the spread of the disease is 

 very much favored by weather conditions where rain and sunshine alternate 

 every few hours. This would indicate that the emission of the zoospore is in- 

 fluenced by the sunlight, and therefore a rapid alternation of rain and sunshine 

 would favor the production of zoospores in large numbers, which being absorbed 

 by the raindrops would be carried by the wind from tree to tree. Neither 

 sexual organs nor oospores were found on the diseased nuts or tree tops, but 

 these organs were observed later in laboratory cultures on inoculated areca 

 nuts and on other species of plants inoculated with the fungus. Attempts to 

 cultivate the fungus from old diseased nuts which had remained in the garden 

 for a year were unsuccessful. The successful inoculation of other plants with 

 areca Phytophthora indicate that the fungus has other host plants in the in- 

 fected area. 



After a comparison of the cultures on artificial media and cross inoculations 

 on various hosts of the areca Phytophthora, the cacao Phytophthora, and P. 

 omnivora, the author decides that the morphological differences are sufficient to 

 separate the three forms. For the areca fungus, P omnivora arecce n. var. is 

 suggested, while the cacao form is called P. theobromw n. sp. 



The natives of Mysore have attempted to control the disease by covering the 

 nuts with dead leaf sheaths which keep off the rain, but this has proved only 

 partially successful. A single application to the nuts of 5:5:50 or 5:5:25 

 Bordeaux mixture to which has been added a sticker consisting of 2 lbs. of 

 resin and 1 lb. of washing soda boiled in 1 gal. of water, in June just before 

 the monsoon, has proved more effective than the covering. The efficiency of 

 the spray seems to depend upon the quantity of sticker used rather than on the 

 strength of the Bordeaux mixture, as 1 lb. of sticker to every 25 gal. of Bor- 

 deaux mixture gave the best results, irrespective of the strength of Bordeaux 

 mixture used. 



A preliminary note on the fungus causing the dieback disease of cacao 

 and of Para rubber, K. Bancroft {Agr. Bui. Straits and Fed. Malay States, 

 9 (1910), No. 12, pp. 475-478). — The author claims to have developed the 

 ascigerous stage of this fungus (Diplodia cacaoicola) on badly diseased stems of 

 the cacao plant, after keeping portions of the stem in a sealed jar for 6 months. 



The perithecia were grouped in a black, erumpent stroma bearing a covering 

 of weak hairs. The perithecial stage of the fungus belongs to the genus Thyri- 

 daria (Sphasriacese), and is described as T. tarda n. sp. 



On the formation of diseased heartwood, E. MiJNCH (Naturic. Ztschr. Forst 

 u. Landw., 8 (1910), No. 11, pp. 533-547, fig. 1; 12, pp. 553-569, fig. i).— The 

 author discusses the causes, formation, properties, and physiological functions 

 of pathogenic heartwood. 



It is stated that the formation of gum and other decomposition products 

 which produce a brown discoloration of the wood known as false heartwood 

 is due to fungus attacks, wounds, oxidation, and pressure changes. The so- 

 called false heartwood is the first stage of decay due to the attacks of wood- 

 destroying fungi, the mycelium of which secretes a brown substance resembling 

 wound gum in the tissues of the wood. This wound, or protection gum, may 

 also be produced by the oxidation of the contents of dead parenchyma cells. 



