Robinson.— Notes on the Genus Tophrina. 165 
arising from the subepidermal network, make their way 
between the cells of the epidermis and become developed into 
asci which, as In the other species, are formed between the 
cuticle and epidermis. In several species each ascus is borne 
on a specialized portion of the mycelium known as the 
stalk-cell. These cells vary considerably in form, being 
sometimes long and slender, cylindrical or obconical, or, on 
the other hand, short and broad with flat and truncate bases. 
Within each ascus generally eight nearly spherical spores are 
formed, but the octosporic condition is often not permanent, 
for while yet in the ascus the spores divide by a process 
closely resembling the budding of the Saccharomycetes. In 
this way the asci frequently become filled with very numerous 
reproductive bodies, sometimes resembling the eight original 
spores, except in their smaller size and rather more oblong or 
oval form, in other cases becoming very minute and bacteria- 
like. The asci of several species are always polysporic at 
maturity, and no eight-spored condition is readily discernible 
in their development. Even in them, however, there seems 
reason to believe that the many-spored form is secondary, 
resulting from spore-division. As the asci grow they raise up 
the cuticle from the epidermis, and at some period, early in 
some cases, near maturity in others, break through to the 
surface. The release of the spores when the asci have not 
been subjected to any violent rupture, to which their delicate 
structure and superficial position render them liable, seems to 
be effected through a rather small orifice at the summit of 
the ascus. 
The presence of a Taphrina is manifested by the host in 
one or more of several ways : namely, by the occurrence 
on the leaves of roundish or irregular blotches, varying in 
colour from yellow to purple according to the species of 
the parasite; by a curling or crisping of the leaves, some- 
times accompanied by a toughening or cartilaginous modi- 
fication of the leaf-texture ; by the swelling out of the softer 
parts of the leaves between the nerves, rendering the surface 
convex on one side and concave on the other ; by deformity 
