176 
lias a very agreeable smell and a fine taste, afterward somewhat astrin¬ 
gent. The mycelium excretes large quantities of water and keeps 
dwelling rooms excessively damp. In decay, the sporophores produce 
a very characteristic disagreeable odor, which is undoubtedly prejudi¬ 
cial to health. Infection may take place either through mycelium or 
spores. The latter are often carried from place to place on clothing, 
tools, etc., which have been used by workmen, especially carpenters, 
in repairing decayed buildings. 
The book seems to have been very carefully prepared, but some omis¬ 
sions are noteworthy, and occasionally one meets a questionable state¬ 
ment. 
Under Gymnosporangium four species are mentioned— G . conicum (juni- 
perinum ), clavariceforme , Sabinw (fuscum ), and tremelloides. The author 
thinks a further investigation of the forms thus far known and de¬ 
scribed is desirable, as the results of some experiments instituted by 
him do not agree with those commonly accepted. No mention is made 
of the labors of Dr. Farlow or of Dr. Thaxter. 
Under bacteria Dr. Hartig urges the commonly accepted view that the 
acid reaction of most plants is unfavorable to their growth and develop¬ 
ment, and evidently thinks they play a very unimportant role in the pro¬ 
duction of plant diseases. They have been found as parasites, he says, 
only in thin-walled, soft parenchymatous tissue, such as bulbs and 
tubers, and here are often preceded by fungi. Even in Waacker’s 
hyacinth disease (the yellow, slimy bacteriosis) u the bacteria do not at¬ 
tack entirely sound, well-ripened bulbs under normal conditions,” but 
only those that have been wounded or previously attacked by fungi, 
especially by a hyphomycetous fungus, which is almost always asso¬ 
ciated with this bacteriosis. In damp places the bacteria enter the 
wounds and cause the rot. The following paragraph on pear blight 
will hardly pass muster, and was certainly not to be expected in a hand¬ 
book published in 1889. All the recent American publications on this 
subject, especially the papers by Dr. Arthur, appear to have escaped 
the author’s attention. 
Recently a disease of pear and apple trees, called blight, bas been described by 
J. Burrill in Urbana, Ill., the cause of which this investigator ascribes to the inva¬ 
sion of a bacterium. The disease appears to bear a resemblance to the tree canker 
( Baumkrebs ) caused by Neciria ditissima, and since in this fungus small bacteria-like 
gonidia are prpduced in great numbers in the bark, it becomes necessary to inquire 
first of all whether this disease has not been wrongly ascribed to a schizomycete. 
Mention is made of- fifteen species of Exoascus , all of which produce 
characteristic hypertrophies. Seven of these species also cause hex- 
enbesen or witchbrooms, and these peculiar growths are also induced 
by various Uredinew , notably by the tecidium ( Peridermium pint) of 
Coleosporium senecionis, and by JEeidium ( Peridermium) elatinum. 
The black-knot of the plum and cherry, Ploicrightia morbosa , is said 
to occur only in North America, but the author thinks it may be in- 
