224 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY 



the epidermis. Mycelium was plainly visible in the surrounding cells 

 and in connection with the black bodies. The cells permeated by the 

 mycelium were dead, and of a reddish colour, this portion being externally 

 visible by the reddish spots on the bark. Having obtained this clue it 

 became necessary to look for the first appearance of the fungus. 



As my correspondent correctly stated, the disease starts first on the 

 one-year-old wood. He undoubtedly had in his mind the canker spot 

 stage which he describes as the disease. But the pathologist has to go 

 farther and must ascertain the beginning of the injury. Abundant 

 evidence was found of the fungus on the rose twigs, where no fissures or 

 splits of the bark were recognizable and indeed where none existed. In 

 the young green wood more or less confluent red-brown to purplish spots 

 were present on the bark. These spots were found in any position on the 

 bark, and were in no way connected with branches, thorns, or buds ; this 

 point is of importance in realizing the nature of the parasite. 



A series of twigs showing the beginning and the progress of the 

 disease was selected and has been drawn from nature in the accompanying 

 illustration. 



Fig. 34 shows at a a young twig of double natural size. On this twig 

 four of the spots, in the natural specimen reddish brown to purplish, 

 are to be seen. At b the upper portion to the cross line of a is 

 enlarged four times and shows the uppermost spot and part of the one 

 below to be covered with minute cracks. At c a few of these fissures are 

 shown enlarged twenty times, when one can readily see their nature. To 

 the left are three cracks through which the round black fungus bodies 

 show pushing through the bark, with an apical opening. More to the 

 right is one of the minute elevations still covered with the intact bark, 

 while to the extreme right a body is just breaking it. This figure 

 represents the appearance of one of the reddish spots in a or b when 

 looked at from above. If a portion of the bark is cut into thin sections 

 lengthways, and one is examined under the microscope, it appears as in 

 figure d. There are eight fungus bodies present, two growing singly and 

 three in each of two groups ; the latter have burst the epidermis, while 

 the former are still covered by it. At e a separated body of the fungus 

 is figured and f represents the same sliced open. In both of these figures, 

 the fine mycelium and the netlike meshes composing the fungus body 

 can be seen. The fungus body contains a large number of exceedingly 

 Bmall spores, and these spores when ripe ooze out of the round opening at 

 the apex of the black conceptacle. At g a small portion of a conceptacle 

 is still more enlarged, and attached to it are a number of fine filaments 

 magnified at h, where the position and the shape of the spores can be plainly 

 seen. At i these spores are highly magnified ; they are oval, transparent 

 bodies, which are figured at different stages of germination at J. 



The fungus belongs to the genus Coniothyrium. Although the 

 Bpeciea of Coniothyrium are generally of saprophytic habit, i.e. living on 

 dead and dying tissues, some are known to "in many cases inhabit 

 living tissues" (Sorauer, Ilandb. d. P/lanzenkrankheite?i, 2nd ed. II. 

 1>. U85). Thus for instance; Coniothyrium concentricum (Desm.) Sacc. 

 is tlx fungus causing the well-known brown spots on leaves of Agave 

 and allied plants. Laubert (cf. Zeitschrift f. Pflanzenkrankheiten, 



