DISEASES OF PLANTS. 57 



Notes on Peridermium cerebrum, and P. harknessii, G. G. Hedgcock {Phyto- 

 pathology, 1 {,1911), No. 4f PP- 131, 132). — The author reports the successful 

 inoculations with seciospores of P. cerebrum from Pinus virginiana to the leaves 

 of several species of oaks, which resulted in the production of the uredinia and 

 telia of Cronartiiimm qticrcuuin. 



Successful inoculations by means of wounds were made with the teliospores 

 of this rust on the young twigs of Pinus divaricata, P. virginiana, P. ponderosa, 

 P. murrayana, and P. sylvest7is. The galls resulting from these inoculations 

 varied in shape from globoid to oblong, and were frequently accompanied by the 

 formation of dwarfed cluster twigs or witches' brooms, especially on P. pon- 

 derosa, P. murrayana, and P. virginiana. 



Attention is called to the close morphological resemblance of Peridermium 

 harknessii and P. cerebrum, and it is stated that if P. harknessii is proved to 

 have its alternate stage as Cronartiuni quercuum, the two Peridermiums are 

 identical. 



Shade tree troubles, G. E. Stone {Massachusetts Sta. Rpt. 1910, pt. 2, pp. 

 52-55). — The author calls attention to a number of troubles of shade trees, 

 particularly of oaks and maples. 



The oak trees examined seemed to be healthy so far as the trunks and larger 

 roots were concerned, but the smaller roots for a considerable distance about 

 the plant were dead. An examination made of the root system showed that 

 there had been a constant dying back of the roots for a number of years, the 

 exact cause of which was not determined. 



The sun scald and sun scorch of maples are described, the sun scald being 

 rather severe in its effect on the trees. Following the drying up of the bark 

 a canker fungus {Nectria cinnabarina) is usually found in the case of the sun 

 scald, and the presence of this fungus differentiates this trouble from gas injury, 

 which is usually followed by profuse outgrowths of Schizophyllum and Poly- 

 sticta. 



The damping off of coniferous seedling's, C. M. Gifford {Vermont Sta. Bui. 

 157, pp. lJi3-lll, pis. 4, figs. 10). — An account is given of investigations on the* 

 damping off of coniferous seedlings, in which the author found that the principal 

 cause of the trouble is a species of Fusarium. Seedlings of white pine, Scotch 

 pine, yellow pine, Norway spruce, and European larch appeared subject to at- 

 tack under unfavorable conditions. The fungus appears to be a native of this 

 country, and is widely distributed. It was repeatedly isolated from the roots 

 of 2-year-old seedlings of the white pine. 



The fungus grows readily in culture media, and fruits abundantly, producing 

 3 kinds of spores. The attack is made through the tender stems of the seedlings. 

 In a short time the stem is weakened, its water supply cut off, and it soon dies. 



The amount of damage due to this fungus varies with temperature and mois- 

 ture, as well as with the reaction of the soil, an alkaline soil greatly increasing 

 the amount of iujury. 



Experiments for the control of the damping off were carried on during the 

 summer of 1909, sterilization of seed beds with steam and various strengths of 

 formalin being tested. The sterilization of the soil by the use of live steam WkIS 

 found less effective than the use of dilute solutions of formalin. The formalin 

 was found to reduce the percentage of germination to some extent, but, even con- 

 sidering the smaller stand, the results obtained from its use were quite satis- 

 factory. In the use of steam, which was by the inverted pan method, there 

 seemed to be a decided effect on the moisture content of the soil. Steamed and 

 unsteamed soils were placed in tubes to determine the effect of steaming, and 

 showed a decided difference in the capillary movement of water after standing 

 for a period of 63 days. 



20296°— No. 1—12 5 



