406 



SCIENCE. 



[N. S. Vol. XV. No. 376. 



plate cultures, made with care from the 

 advaucing margin of the diseased area, give 

 only bacteria and generally pure cultures 

 of a rod-shaped motile Schizomycete. 

 Neither fungi nor burrowing insects are 

 present. The colonies appear in the agar 

 plates in from twenty-four to thirty-six 

 hours. The surface colonies grow rapidly, 

 are nearly round, slightly convex, having 

 a milky color, shining surface and entire 

 margin. The imbedded colonies remain 

 much smaller, are mostly spindle-shaped 

 and have a brownish tinge. The organism 

 grows rapidly on nutrient, slant agar, and 

 •on steamed potato, carrot, parsnip, salsify, 

 beet and onion. It does not discolor the 

 medium upon which it grows; it develops 

 slowly in alkaline gelatin ; the stab cultures 

 are beaded in form, and the gelatin is not 

 liquified. Milk is coagulated rather rapidly ; 

 blue litmus milk is changed to red and 

 eventually faded to white. Nitrates are 

 reduced to nitrites. The organism grows in 

 the closed end of fermentation tubes con- 

 taining peptonized beef bouillon with 5 per 

 cent, grape sugar, but without formation 

 of gas. Diseased plants have been treated 

 with lime, sulfur and dilute formaline, 

 with some success in controlling the disease, 

 but the best treatment found thus far con- 

 sists in changing the soil in the calla bed 

 or in growing the plants in pots, and in 

 the proper management of the greenhouses. 



A Disease of the American Ash: Dr. Her- 

 mann VON ScHEENK, Shaw School of 

 Botany. 

 A disease of Fraxinus Americana caused 



by Polyporus fraxineus was described. 



Attention was called to the large per cent. 



of living trees affected with this disease 



in localities where the ash is present in 



large numbers. 



Yegetative Reproduction in Leptolejeunea: 

 Professor A. W. Evans, Yale University. 

 Certain species of the epiphyllous genus 



Leptolejeunea reproduce themselves largely 

 by means of leafy propagula, which repre- 

 sent modified branches. This type of vege- 

 tative reproduction, although known in 

 several mosses, has not before been recorded 

 for the hepatics. The first leaves and un- 

 der leaves of the propagula show curious 

 modifications, and the most remarkable of 

 these are found in the underleaves, which 

 develop disc-shaped suckers instead of the 

 usual clusters of rhizoids. By means of 

 these suckers, the propagula are able to 

 attach themselves quickly to the smooth 

 leaf -surface upon which they grow. 



Observations on Pterygopliora: Professor 

 Conway MacMillan, University of Min- 

 nesota. This paper will be published in 

 full in Minnesota Botanical Studies. 

 Pterygophora grows much larger in the 

 Straits of Fuca than reported in systematic 

 works upon the kelps. It has been found 

 with stipe three meters in length and a 

 decimeter in thickness. Secondary thicken- 

 ing, in Lessonia apparently limited to the 

 stipe, takes place in Pterygophora in both 

 hapteres and stipe, producing rings of 

 groAvth in each of these organs. Secondary 

 thickening in the haptere differs from that 

 in the stipe. In the former the ringed ap- 

 pearance is principally due to succession of 

 cell layers differing in contents; in the 

 latter the ringed appearance is due to suc- 

 cession of cell layers in which the elements 

 are of different size and shape. A cross 

 section through the growth-ring in the stipe 

 of Pterygophora recalls similar sections 

 through the stem of Gymnosperms. The 

 siibstance which by its varying abundance 

 in successive cell layers gives rise to the 

 ringed appearance in cross sections of old 

 hapteres is related to that which has been 

 called fucosan and appears to be poly- 

 saccharid in character. Pits, in the 

 strengthening tissue and tissue of growth- 

 rings of the stipe, are abundant upon the 



