246 
W. B. Mercer, 
growth. The resemblance to the cross-section of an oak stem is striking, 
the vessels of the wood being here represented by pycnidia. 
Mouse-grey aerial or “luft“-mycelium is formed scantily all over 
the dish, being most plentiful where the layer of agar is thickest; the 
amount varies with temperature, cultures kept at 12° C developing con¬ 
siderably more than those kept at 19° C, or 28° C. The general growth 
on other agar media which have been used, viz-Salep 1 ), Horse-dung 2 3 * ) 
and Calla-lesd' 6 ) is very similar to that on plum agar. Concentric rings 
of growth occur on all. On Salep agar the mycelium is rather thinner 
than on any of the others (Fig. 1, y) and it becomes divided into very 
short cells with age. 
Grown in tap water in moist chambers the fungus produces very 
thin, but otherwise normal mycelium; pycnidia are produced very slowly. 
5% Gelatine containing various food stuffs proved also a fairly satis¬ 
factory medium, though growth was in all cases slow. Very broad (8 ja) 
hvphae were produced on that to which 5% Lecithin had been added 
(Fig. 1, 8). 
Twigs of various trees cut up and sterilized were also inoculated 
with the fungus. It was found that the mycelium penetrated right through 
the wood, running mainly with the grain; on the outside, pycnidia were 
produced in abundance. The greatest irregularity in the cells of the 
mycelium was met with in tube cultures on potato. The amount of oil 
secreted in the hyphae was also striking here. In some cases the cell 
lumen was completely filled with this substance (Fig. 1, p). 
Various other solid media were tried e. g. Banana, Carrot, 
Radish, Rhubarb, Apple, Asparagus — but the growth presented 
no marked peculiarities on any of these substrata. 
2. The pycnidia. 
These are typically round or pear shaped, with a circular mouth; 
but there are very great variations in size and shape on all media. They 
may be oval, or almost linear, or highly irregular in outline, while the 
diameter varies between 25 /a and 200 ju. Taking however those produced 
in cultures on Calla - leaf as the most normal (Fig. 1 , io), the diameter 
when fully ripe may be put at 120—150 ju, that of the mouth at 20 to 
]) Salep-agar. 30 g agar, purified as before, were boiled for half an hour 
with a litre of water. 9 g Salep powder (Bernard, Rev. Gén. de Bot. 1904, 16, 408) 
were likewise boiled half an hour with a similar quantity of water, made up again to 
1000 ccm, and mixed with the agar solution. Further food materials, according to 
Klebahn’s method, were then added, viz: 
Trace. 
Glucose 1 g NH 4 N0 3 
Tartaric acid 0,2 g 
KH 2 P0 4 0,2 g MgS0 4 
The mixture was then boiled for a further half hour, filtered, and stored in the same 
manner as with plum agar (vide Klebahn, Jahrb. f. Wissensch. Bot. 1905, 41, 488). 
The medium is practically neutral. 
2) Horse-dung-agar. A decoction of horse dung to which 2°/ 0 of pore 
agar was added. 
3) C« //a-leaf-agar. Abont 10 g of Calla-\ea.i boiled with 100 ccm water and 
2 g agar added to the filtrate. 
