VOL. Iv. | Reviews. 409 
Die Parasitischen Exoasceen. A Monograph. By R: Sapx- 
BECK. Hamburg, 1893. In the above monograph is presented 
a very complete and accurate account of the peculiar group of 
Fungi, the Exoascee. The members of this family are fungi of 
extremely simple structure, and some of them are parasites that 
caus? serious trouble by their ravages. Probably the most 
familiar species is Exoascus deformans (Berk.) Fuckel, the cause 
of the well-known disease of peach trees popularly called ‘‘ leaf- 
curl.’? When the trees are severely attacked they sometimes 
are almost completely stripped of their leaves, resulting in a 
serious check to the tree’s growth. 
The first section of Professor Sadebeck’s monograph deals 
with a comparative study of the development and biology of the 
parasitic Exoascezee. Although many experiments were made 
with various species, none of the attempts to grow the spores 
upon artificial culture media were entirely successful, and in no 
cases was he able to produce spore-bearing plants in this way. 
In some instances, however, he was able to follow the penetra- 
tion of the host by the germ-hypha of the parasite, and to trace 
its development within the host. The species especially studied 
were ELxcascus Tosquinetit (West) Sadeb., £&. epiphyllus Sadeb., 
Taphrina Sadebeckit Johans., as well as several other species of 
Taphrina. In the species of Axoascus the mycelium is peren- 
nial, and this insures the perpetuation of the fungus, even if for 
any reason the spores should fail to germinate. 
The asci open by a cleft at the apex, and the spores are 
violently ejected by the strong contraction of the side walls of 
the ascus which are in a state of tension before it opens. Some- 
times instead of the ordinary spores, yeast-like conidia are 
produced within the ascus, and in case the conditions are un- 
favorable for the formation of either spores or conidia, e.g 
in very rainy weather, the asci form directly yeast-like conidia 
by budding. : : 
Sadebeck separates the parasitic Exoasces into the genera 
Exoascus Fuckel, Taphrina Fries, and Magnustella Sadeb. 
The first genus is characterized by the perennial mycelium and 
the fact that the whole mycelium, or at least that part under the 
Cuticle of the infected leaf, breaks up into cells that develop 
directly into asci. ‘Twenty-one species are given. 
