NEEDLE-CAST. 689 



of the needles, and the lower parts of plants suffering most, 

 and above all, from the fact that the disease frequently appears 

 in a single night, and is much commoner in broadcast sow- 

 ings than in natural regeneratiorr-areas. Hess has frequently 

 observed the needles to have been attacked in every plant 

 on a nursery-bed, after one night's hoar-frost succeeded by 

 a sunny day, and this altogether excludes the action of the 

 fungus as cause of the disease. Moreover, infection by the 

 fungus, which is favoured by heat and damp, would be easier 

 under a shelterwood than in the open, which is not the case. 

 The Lophodermium is, however, widely spread as a saprophyte 

 on dead needles of pines, as well as on those of the spruce and 

 juniper. 



1). Frost Needle-cast. 



G. Alers* and Nordlingert have proved that the disease is 

 frequently due to refrigeration of the plants on unprotected 

 soil free from snow, by radiation from the soil-covering, and 

 this opinion has been adopted by most practical men. Generally 

 autumnal frost is the cause, and late frost is not injurious, 

 except when there is a great difference between the night- 

 and day-temperatures. The fact that on older plants only the 

 lower branches lose their needles points to frost as the cause. 



Frost needle-cast is common after wet, cold summers, during 

 which the young shoots of the plants have not been properly 

 lignified. Only late frosts can account for the needles turning 

 red in the spring, but experience has shown that they are not 

 nearly so destructive as early frosts. The fact that needle- 

 cast is so prevalent on clearings, in depressions and valleys, 

 and on uncovered ground where there is no obstacle to radiation, 

 renders it probable that in many cases frost is the cause of the 

 disease. 



c. Dry Needle-cast. 



The drying-up theory of the origin of needle-cast was 

 first published by Ebermayer,! who, during the progress of 

 his observations of soil-temperatures in the Bavarian forest 



* Alers, " Centrlbl. fr. das ges. Frstw.," 1878, p. 132 ; 1893, p. 81. Also 1880, 

 p. 156 ; 1882, p. 159 ; 1883, p. 259. 



t Nordlinger, " Krit. Blttr. fr. Frst. u. Jgdw.." vol. xlvi., 1863, p. 185. 



| " Die Physikalischen Einwirkungen des Waldes in der Abhandlung," " Thar. 

 Frstl. Jhrbch.," vol. xxxiv., 1884, p. 158. 



F.P. Y Y 



