Pflanzenkrankheiten 
37 
those of other workers reviewed in the earlier part will show that the 
enlarging, changing of form, and dividing of the nucleus, the changing of 
the composition of the cell walls, the reduction in the amount of chloro¬ 
phyll, and other changes in the normal content of the leaf cells are all 
duplicated in other organs affected by destructive agents.*’ These changes 
are usually only variations of natural processes, and are not phenomena 
that are known only in pathologic tissues. No nuclei were noted in actual 
process of division, but in a few instances there was some evidence of 
abnormal division. In several cases granular deposits were found in 
various cells in the diseased regions only. It was not always possible to 
determine which constituents of the host cell first showed the effect of 
fungous invasion. The effects of rust upon leaf tissue are similar to those 
of gall-producing insects: the rust seems to stimulate the tissue rather 
than to retard its growth. The varied effects of fungous invasion upon 
the protoplast are described. With the attacks of parasitic fungi on leaves 
the effects are varied, depending upon the species of the host and of 
fungus. The virulence of the parasite and the degree of resistance of the 
host are the chief factors involved. In some of the diseases described, 
in which the tissue is killed and badly disorganised, few if any cytologic 
changes are to be noticed. The reason for this seems to be that the 
virulence of the fungus is relatively so great that the cells of the host 
are killed without having time to react to any stimulus. Taken alone, 
an excessive enlarging of a portion of a plant is not sufficient evidence 
of the degree of parasitism. In the leaf-inhabiting fungi, so far as studied, 
the mode of attack seems to be through the aid of some substance in¬ 
jurious or stimulative to the host cells. J. Ramsbottom (London). 
ERIKSSON, J., Fungoid diseases of agricultural plants. (London, 
Baillière, Tindall & Co., 1912, 208 + XV pp., 117 illustr.) 
This book has been translated from the Swedish by Anna Molander. 
In the author’s preface he tells us that the primary object of the book is 
to be a practical guide for planters, to enable them to recognise, pre¬ 
vent and combat with the diseases: hence historical and literary facts 
generally have been omitted. The diseases are arranged according to the 
fungus causing the disease, each group of fungi having a chapter devoted 
to it. This chapter opens with a short description of the principal points 
of the group and then treats the important diseases in detail, and those 
of less importare very shortly. Protective measures are clearly stated 
in the case of the more important diseases. The book is very well illu¬ 
strated, three illustrations in connection with the Uredineae being coloured. 
There is an interesting chapter on “Unexplored diseases”. Another chapter 
is devoted to an account of general protective measures against diseases. 
There is an appendix of 19 pages giving a table of the fungoid diseases 
of agricultural plants arranged according to their host plants. 
J. Ramsbottom (London). 
Brix, f., p ractische Erläuterungen über Rosenkrankheiten, 
Rosenschädlinge und deren Bekämpfung. („Flora“, Kgl. Sächs 
Ges. f. Bot. u. Gartenbau in Dresden, Sitzungsber. u. Abh., N. F., 
1910/11, 15, 56—64.) 
I. Rosen mehl tau: Beschreibung der Krankheit. Sicherstes Gegen¬ 
mittel ist der Ventilatoschwefel. Das Schwefeln ist stets nur an sonnigen 
