juiyis. I9IS Ascochyta Clematidina 333 



taught the nurseryman that supported vines, owing to the better venti- 

 lation they receive, do not die as readily as those left on the ground. 

 They make a vigorous growth, and yet when about to bloom they may 

 suddenly die. It is at this stage that the disease first attracts the atten- 

 tion of the nurseryman, though in reality it was on the plants while 

 they were still in the greenhouse and was there overlooked. Plate LIU, 

 figure I, shows a plant free from leaf-spot, yet girdled by the fungus 

 lurking in the stub a, which in ordinary practice is not removed. Plate 

 LIII, figure 2, is a reproduction of another vine of C. jackmanni that had 

 many pycnidia of A. clematidi'na on the old stub. After the removal 

 of this stub some of the discolored tissue still remained. The new shoot 

 formed is wilting, and the split stem shows discolored fibrovascular 

 bundles from which A. clematidina was isolated. In advanced stages 

 the roots may disintegrate similarly to that shown in Plate LI I, figure i. 

 The spots on the leaves of C. jackmanni resemble those found on C. pani- 

 culata, C. recta, and C. virginiana. 



ISOLATION OF THE CAUSAL FUNGUS 



By previous writers the dying of clematis plants has been assigned to 

 various factors, but none have discovered the primary cause. The dying 

 of the leaves owing to lack of light, the breaking of the vine by strong 

 winds, and injury by nematodes are factors that have been eliminated as 

 primary agencies, while the constant association of A. clematidina points 

 to it as the causal organism. The fungus can be readily isolated by the 

 poured-plate method, using the spores from a crushed pycnidium, by the 

 use of sterile leaf tissues, or by the use of free-hand sections of diseased 

 material. The last-named method consists in making free-hand sections 

 under as sterile conditions as possible by sterilizing the outer tissue and 

 the instruments. If such sections show mycelium they are transferred 

 to sterile media. Some have maintained that no mycelium can be seen 

 in the decayed tissue, but the writer has observed in the tissues 3 to 5 

 mm. from the boundaries of the lesions mycelium which in plate cultures 

 proved to be that of the causal organism, A. clematidina. 



A . clematidina grows well on the media generally used in the laboratory. 

 It grows at about the same rate on nutrient glucose agar, oatmeal agar, 

 bean pods or stems, moist oats, and com meal, producing pycnidia in 

 five to seven days. These pycnidia may show a pink tinge at first and 

 later turn brown. The fungus grows less vigorously on corn-meal agar, 

 potato agar, starch agar, sugar-beet plugs, apple twigs, and sterile raw 

 carrot. Oatmeal and starch agar are at first turned green, but later take 

 on a brown color. On starch agar the mycelium penetrates the medium 

 and forms chlamydospores, as shown in Plate LII, figure i. These are 

 thick-walled, green-brown bodies filled with oil globules. When placed 

 in water, they germinate readily. 



