754 



SCIENCE 



[N. S. Vol. XXXI. No. 802 



the perithecium being burst off, exposing all the 

 asci at one time. 



The former is doubtless the natural method, 

 but in many eases the number of asci preparing 

 for action at one time may be greater than can 

 be accommodated by the ostiole, and the expansive 

 force bursts off the upper part of the perithecium. 



By placing glue-coated slides at various heights 

 over moistened leaves, some data were obtained as 

 to the height to vifhich ascospores may be dis- 

 charged. This was not found to exceed 1.5 cm., 

 and very few reached this height. In a similar 

 manner it was determined that from a portion 

 of leaf 1 cm. square 5,630 spores were discharged 

 in 45 minutes. In an orchard set 40 feet each 

 way, the surface of which was covered with fallen 

 leaves, if no limiting factors were considered, 

 there might be at this rate 8,107,200,000 asco- 

 spores to each tree discharged in a period of 45 

 minutes of wet weather. 



During the winter of 1909, leaves examined at 

 different dates showed that, by February 26, the 

 perithecia had formed, in the asci of which was 

 as yet no evidence of spore formation. Even at 

 this stage, when pricked out in water on a slide, 

 dehiscence of the perithecia would sometimes 

 occur, without extrusion of the asci. 



By March 20 immature hyaline spores had 

 formed. On leaves kept in moist chambers in the 

 laboratory since February 27, they were much 

 more advanced, some spores being sufBciently 

 mature to be discharged. 



Infection of leaves was repeatedly induced by 

 inoculation with ascospores. The method of in- 

 fection was studied and camera lucida drawings 

 showing the germ tube piercing the cuticle were 

 obtained. The period of incubation varied from 

 eight to fifteen days. 



It seems probable that aseospore infection is, 

 in most cases, largely responsible for early at- 

 tacks of scab on leaves and petioles. The writer 

 was called to diagnose a case in western New 

 York, in which this fact was strongly evident. 

 With one exception every orchard in the imme- 

 diate vicinity had a very severe attack of early 

 leaf infection. On talking with the owners, it 

 was learned that the above exception was the only 

 case in which the fallen leaves had been plowed 

 under the fall before. An examination of those 

 leaves remaining showed an abundance of peri- 

 thecia. 



Polystictus hirsutiis as a Wound Parasite on 

 Mountain Ash: Dr. Jas. B. Pollock, Univer- 

 sity of Michigan. 



At Ann Arbor, Mich., two mountain ash trees 

 were for several years under observation, each 

 tree having one of its main branches partly dead, 

 and in each case the dead branch was covered in 

 part by sporophores of Polystictus hirsutus Fr. 

 The diseased condition was progressive in both 

 trees for several years, the trees gradually dying 

 off, and both trees were removed before they were 

 completely dead. Observations were made on one 

 of them when it was dug up, and the decay of 

 the wood had extended from the dead branch into 

 the main trunk, to a point below the surface of 

 the soil in which the tree stood. This decayed 

 heart wood was filled with a white mycelium. 

 Pieces of this wood were placed in moist cham- 

 bers, and after a month or two fruiting bodies 

 developed which showed it to be the same fungus 

 whose fruiting bodies developed for several suc- 

 cessive years on the dead branch fifteen feet above. 



The observations seem to show that this fungus 

 not only is a wound parasite, destroying the dead 

 heart of a tree, but that it slowly and progress- 

 ively attacks the cambium, gradually killing off 

 this species of tree. 

 Notes on Plant Diseases in Cuba: Professor 



William Titus Hobne, California Agricultural 



Experiment Station. (Read by C. L. Shear.) 



A list of publications on plant pathology 

 arising from the writer's work at the Cuban 

 Experiment Station is given, and the following 

 diseases of the principal cultivated plants are 

 discussed: sugar-cane troubles — drouth, exhausted 

 soil, moth borer and root fungus; tobacco — damp- 

 ing off, leaf spot and root disease; banana — an 

 undetermined disease; mango and aguacate: 

 mango — blossom and tip blight (GUesporium) , 

 aguacate — destructive disease not determined. 

 Also diseases of citrus fruits and vegetables. 



Failures due to lack of adaptation or unappro- 

 priate periodicity are also mentioned and edu- 

 cation and improved agricultural practise sug- 

 gested as necessary to utilize the results of the 

 plant pathological investigations which have been 

 made. 

 Txoo Diseases of Cosmos: Mr. F. C. Stewart, 



New York Agricultural Experiment Station. 



(Read by title.) 

 A Ouhan Ban<ina Disease: Dr. Eewin F. Smith, 



Department of Agriculture. 



!My attention was first called to this disease in 

 December, 1908, by Mr. Home, of the Cuban 

 Experiment Station, who requested me to study 

 the cause of the disease. Up to this time I have 

 been unable to visit western Cuba where it pre- 



