126 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



In those cases where the fall is due to the direct action of 

 frost, or of cutting cold winds — i.e., where the leaves are killed 

 by the sudden abstraction of heat from their tissues — keen 

 observers have found that those basal parts of the needles " 

 which are enclosed in and protected by the sheathing- scales of 

 the short branches (''tufts") may remain fresh for some time after 

 the exposed parts have turned brown and shrivelled up. 



In the second class of cases, however, no such partial 

 shrivelling of the leaves is seen ; the tissues dry up all along 

 the " needles," from tip to base completely, and this is because 

 they have been killed by drought — either because the roots in 

 the frozen soil cannot supply water to replace what is being 

 transpired in the bright sunshine, or because the weather is so 

 hot and dry that there is not enough water in the immediate 

 environment at all. 



Different as are the above causes of premature leaf-casting, 

 there are still others, of v/hich the following is the most prevalent 

 and difficult to deal with. The leaves turn yellowish, with 

 brown and purplish spots and patches on them, and fall in 

 showers as before ; but this time the disease is found to be 

 epidemic in character. Towards the end of the summer 

 numerous tiny black spots may be observed on the dying and 

 dead leaves, and these are the spermogonia of a definite fungus 

 {HystermmPinastri, one of the PhacidiacecB of the Discomycetes). 

 In wet seasons, or if the leaves be kept moist through the 

 winter, the higher fructifications and asci may be obtained. 



Eesearches have shown that Goppert* was quite right, so 

 long ago as 1852, in attributing this epidemic to the ravages of 

 the mycelium of the above fungus ; the hyphae invade the leaf- 

 tissues during wet seasons, kill the cells, and so bring about the 

 browning of the " needles." When large quantities of needJes 

 have been thus ruined, they suddenly fall in the showers which 

 bring dismay to the forester and horticulturist, and give the name 

 (shedding — scliiltte of the German foresters) to the disease. 



These are not the only causes of premature leaf-casting in 

 Conifers, but they are good examples of the commonest types, 

 and I have brought them forward here to show you how very 

 easy it is for anyone unacquainted with the facts to draw 

 erroneous conclusions as to the causes of the phenomena ; and 

 * " Verliandl. d. schlesisclien Forstvereins," 1852, p. G7. 



