1900 THE HAUSTORIA OF THE ERYSIPHEA: 159 
Some difficulty was experienced in sectioning those leaves which 
contain large crystals of calcium oxalate, as Corylus and Xan- 
thoxylum, because these crystals frequently caused the destruc- 
tion of the ribbons. For that reason, the side of the leaf bearing 
the fungus was usually turned toward the knife in cutting, unless 
the fungus was amphigenous. 
All staining was done on the slide. Wisselingh (37) finds in 
fresh material that chitin is present in many places as one con- 
stituent of fungus cellulose. In the Erysiphee, chitin appears 
in the perithecia, appendages, mycelium, conidia, and conidio- 
phores. He does not mention haustoria in this connection and 
finds no characteristic stain for walls containing both cellulose 
and chitin ; congo-red, however, in neutral and ammoniacal solu- 
tions, stains pure cellulose intensely, while if chitin is present 
also, the color is not dark, unless the chitin be transformed to 
mycosin.' Mangin (21) found pectin quite generally present in 
fungus cellulose and employed ruthenium-red as a characteristic 
stain. Wisselingh (37, p. 632) was able to remove the pectin 
from cell walls containing it. Mangin did not investigate this- 
question and Wisselingh denies the presence of pectin in the 
Erysiphee. My own results confirm this view. With ruthenium- 
red the fungus would not stain at all, though the middle lamellz 
of the cells of the host-leaf gave the pectin reaction. The most 
characteristic staining obtained in the fungus, in the use of congo- 
red (neutral and alkaline solutions) and methylene-blue (neutral 
and acid solutions), was an intense staining of the ascus wall in 
the perithecium. Wisselingh does not mention this as a part 
containing chitin, and, since the remainder of the fungus seemed 
to give the chitin reaction by refusing to stain deeply with 
congo-red, it is possible that the ascus wall is composed of pure 
cellulose. 
The walls of the haustoria do not show any reactions to 
stains that would indicate that they contain any different 
material from the remainder of the fungus. Flemming’s well- 
known triple stain, safranin, gentian-violet, and orange-G, proved 
*He used a modification of Gilson’s method (16). 
