8 
W. J. Dowson, 
for the most part short and crowded together, so that the colony always kept its star 
shaped outline determmind once and for all by the germ hyphae. On the sixth day 
the conidiophores were still without prolongations; but chains of two spores were 
occasionally seen ; some times a head bore two spores side by side, in which case 
it was noticed that one of the two spores was placed upon a little side branch (see 
figs. 29.?, 39). The general colour was greyish. In a 15 days old culture the conidio¬ 
phores were very numerous, and consisted of as many as seven prolongations of the 
original primary head, and as many as 14 spores (fig. 44). Very little sunken mycelium 
was present, and the growth consisted chiefly of aerial and surface mycelia besides 
the numerous conidiophores. 
2. On Glucose agar. 
On the third - day the colonies were just visible to the unaided eye as very 
small stars of irregular outline. On the fourth day the aerial hyphae and young 
conidiophores had begun to emerge from the agar. On the fifth day the central 
portion of the colony had taken on a grey-green colour; the hyphae of which the 
mycelium was composed was not wavy, but sharply bent here and there at well 
marked angles. In petri-dish cultures of the same age it was noticed that the 
central portion was yellowish as distinct from the grey-green in the hanging-drop 
cultures. It was noticed that the individual cells of which the sunken mycelium was 
composed were shorter than those produced in plum-juice agar. A colony 13 days 
old appeared very nearly black in colour to the unaided eye. 
3. On Meat-extract agar. 
The grow'th was very similar to that on salep agar; but neither conidiophores 
nor their prolongations were so numerous, not more than four spores were observed 
on any one spore-bearing hypha. The characteristic grey, spirally — coiled hyphae 
were present as before (see photomicro B). It was observed that whenever these 
aerial hyphae touched the surface of the agar, which they did in a few cases, that 
at this spot the hyphae branched, and sent out hyphae into the substratum. The 
mycelium increased in mass, but very little in area, and the hyphae of which it 
was composed were packed closely together. 
4. On Plum-juice agar. 
The colonies after three days growth were just visible to the unaided eye, and 
could be destinguished from those of H. Betae of similar age by their more regular 
outline. As on Meat-extract and salep agar the outline of the mycelium was 
determined by the germ-tubes becoming the main hyphae. On the fourth day the 
sunken mycelium began to turn brown, and on the sixth had become olive-green in 
colour. Many more conidiophores were produced than by H. Betae on the same 
medium. The colony finally became dome shaped. It was observed in cultures of 
more than a week old, that many of the spores germinated in situ upon the conida- 
bearing-hyphae which continued to grow vegetatively and ended in a sharp pointed 
structure, calling to mind the conidiophores of Helminthosporium and of Heterosporium 
Syringae as observed by Klebahn 1 ). These vegetative growths were never observed 
to bear spores. % 
It may be well here to summarise some of the results obtained from the 
hanging-drop-cultures, as it will be seen that one and the same form growing upon 
different media, but otherwise under the same conditions presents well marked 
differences in colour of the mycelia, its amount, and nature, so much so that at 
first sight the cultures appear to belong to separate and distinct forms. A culture 
for instance, of H. Betae upon glucose is very different even to the unaided eye, from 
a culture of the same form upon maltose-agar. Again the absence of the coloured, 
vertical hyphae in cultures on plum-juice-agar produces a very conspicuous difference 
when taken in conjunction with the fact that such hyphae were formed upon all the 
other media tried. 
Summary. 
Heterosporium Betae. 
1. Upon glucose agar. 
The germ hyphae are longer and more branched than upon plum-juice-agar; 
but the aerial hyphae are not so long. The final colour of the sunken mycelium is 
1) Krankheiten des Flieders, S. 12. 
