158 BOTANICAL GAZETTE [ MARCH 
in weak nutrient solutions. He was able to obtain appressoria- 
like organs where the filaments came in contact with the cover 
glass, but the germinating tubes had a very limited growth and 
soon perished. His results with the leaves indicated chemo- 
tropic reactions in the filaments. As a whole his experiments 
on the Erysiphez were not directly successful and they bear little 
relation to the haustoria themselves. Reference will be made to 
this paper again in discussing Phyllactinia. 
Galloway (15) devotes a short paragraph to haustoria in an 
account of his observations on the development of Uncinula 
spiralis and figures them in much the same way as De Bary. Har- 
per very briefly describes the haustoria of Sphaerotheca Castag- 
net, and he gives but a single figure (17). Palla (24) has recently 
investigated Phyllactinia on Berberis and Corylus, but he con- 
cerns himself rather with the habit and structure of the mycel- 
ium than of the haustoria. For the minute points of structure 
his methods are inadequate, as he himself intimates (p. 70). 
It will be seen from this brief résumé of the literature that the 
minute structure and especially the development of the haustoria 
are almost entirely unknown. 
METHODS. 
Four fixing solutions were experimented with and their 
respective merits were compared: Flemming’s fluid (stronger 
solution), Merkel’s solution, chrom-acetic acid (0.7 per cent. of 
the former and 0.3 per cent. of the latter), and a saturated solu- 
tion of mercuric chlorid in 1 per cent. acetic acid. Flemming’s 
fluid proved the most reliable and satisfactory. In those cases 
in which it blackened the tissues, the sections, after having bee 
attached to the slides, were bleached for twenty-four hours 1” 
hydrogen. peroxid before staining. Merkel’s solution was fre- 
quently satisfactory, but it proved hardly as reliable as Flem- 
ming’s. The other two solutions were far less useful. The 
sections of leaves were cut 6—7 w in thickness and were fixed to 
the slides by the well-known albumen and distilled water methods. 
They were cleared in clove oil and mounted in Canada balsam. 
