64 
Smith.—On Direct Nuclear Divisions in the 
Identification of the Sfecies. 
The species does not correspond exactly with any of those described 
in Rabenhorst’s ‘Flora', and it is considered to be a hybrid which shows 
affinities to at least three recognized species, but resembles most closely 
dioica , of which it is considered to be a variety possessing stouter hyphae 
and fewer antheridia. The antheridia are produced on separate branches, 
thus indicating that it is very closely allied to that species. The relations of 
its characteristics to various species are given in the following table : 
Size of hyphae 
Form of oogonium 
Size of oospheres 
Number of oospheres 
Antheridia 
17 - 30 / 
Spherical to cylindrical, no 
spines or warts 
18- 20 /x 
8-26 
Not very numerous, always 
diclinous 
S. torulosa and Lechmere’s sp. 
S. torulosa, S. dioica , and 
Lechmere’s sp. 
Any species. 
S. dioica and A. torulosa. 
S. dioica. 
Technique. 
The discovery of a good fixative was a matter of some difficulty. The 
outer walls of the hyphae are very thin, and unless fixation was instantane¬ 
ous plasmolysis resulted, with the consequent shrinkage of the cytoplasm. 
The most satisfactory liquids were Merkel’s solution and a modification 
containing acetic acid : 
Acetic acid (5 per cent.) .... 100 parts. 
Platinic chloride (1 per cent.) ... 5 parts. 
Chromic acid (1 per cent.) . . . . 10 parts. 
This gave excellent results, both in quickness of killing and in preservation 
of the nuclei, especially when used at 70° C. 
During the fixing and washing processes it was most convenient 
to handle the material while still attached to the fly. After the flies had 
been washed in 50 per cent, alcohol for six hours they were placed in water 
and the mycelium scraped off with needles. At this stage the hyphae were 
fixed to the slide, by using a thin film of Meyers fixative; very little was 
required, as an excess absorbed the stain and thus lowered the value of the 
preparations. The hyphae were placed in a drop of water on the prepared 
slide and dried in an incubator. Care had to be taken to prevent all the 
water from evaporating, though if too much water were left all the hyphae 
floated off again. At the right moment the slides were placed in 70 per 
cent, alcohol for two minutes, thus permanently fixing the material to the 
glass. From the 70 per cent, alcohol they were placed in water and were 
then ready for staining. By this method the long delay experienced by 
Hartog was obviated. 
Those who studied the sexual organs used microtome sections, but 
