346 Wisconsin Academy of Sciences, Arts, and Letters. 
three to seven microns in thickness. Flemming’s triple stain was 
used for all preliminary studies, but all results with it were con¬ 
firmed by the use of Heidenhain’s iron-alum haematoxylin. 
Observations 
These studies show that the mycelium of Taphrina coryli Nishida 
may infect all parts of the leaf and the cortex of the youngest 
twigs of Corylus americana, as an intercellular parasite. It is 
found between the cells of the cortex of a one-year-old twig, but it 
is not found in older branches; apparently it grows out into the 
new cortex each season. In a young diseased leaf, the fungus may 
be traced along the veins, between spongy parenchyma and palisade 
cells, and frequently a layer of short thick cells is found between 
the cutin and the epidermis. In an older, badly diseased leaf, 
every available intercellular space is occupied by the fungal 
hyphae, and in addition, portions of the upper and lower surfaces 
of the leaf may be covered with asci. Instead of the classification 
of the mycelium given by Pierce (1900) for Exoascus deformans, 
namely vegative, distributive, and fruiting hyphae, the writer will 
refer to only vegetative and fruiting hyphae; meaning, by the 
latter, asci and subcuticular ascogenous cells, and by the former, 
all other mycelia belonging to the fungus. 
The vegetative cells of Taphrina coryli form long filaments, par¬ 
ticularly where they follow the vessels in the leaves and between 
the palisade cells. In the air spaces between the spongy paren-« 
chyma cells, they broaden out and frequently branch. This dicho¬ 
tomous branching has been described by Pierce for Exoascus de¬ 
formans, and is quite characteristic of Taphrina coryli (fig. 1). 
Each vegetative cell is long, cylindrical, thin-walled and contains 
a fine granular network of cytoplasm with either one or, more fre¬ 
quently, two nuclei (fig. 2). In a binucleate cell, the nuclei are 
small, each containing one prominent nucleole and a very small 
quantity of chromatin (fig. 3). This binucleate condition arises in 
the vegetative cells, and never in the ascogenous cells, of Taphrina 
coryli Nishida. Division figures were seen a number of times in 
the vegetative cells (figs. 4, 5). The spindles and centrosomes are 
extremely small, as are also the masses of chromatin material which 
pass to each pole. Ikeno observed binucleate cells in all forms of 
Taphrina studied by him, and Dangeard (1894) held that the 
mycelial cells of Exoascus deformans were originally binucleate 
