f 
NOTES AND ABSTRACTS. 237 
though the soil and climate are very unlike those of its native country. Abies 
nobilis is quite unhurt by the severest frost, and it is never injured by the heaviest 
snowfall ; but it will never attain much size, though it grows better in the High- 
lands up to about 1,000 feet than it does in the south at low elevations. — A, D„ W t 
Plant Pathology, Problems of. By F. L. Stevens (Bot. Gaz. vol. lxiii. No. 4, 
April 1 91 7, pp. 297). — The author gives a survey of modern pathological work, 
and points out the need for a classification of plant diseases which should em- 
phasize the relationships of conditions which it is of service to know. The 
following suggestions towards such a classification are made : — 
I. The parasite living in the sap or in cavities or parts devoid of living 
protoplasm : 
(a) Wilt diseases due to mechanical stoppage of vascular bundles by parasites, 
t.g. B. solanaceavum. 
(b) Diseases caused by disintegration of xylem structures, e.g. various 
wood rots, Hydnum, Fomes, &c. 
II. The parasite for the most part of its life drawing its nutriment from 
host cells that are still living : . 
(a) Endocellular parasites — the strictest type of parasitism, e.g. Synchytrium. 
(b) Diseases due to parasites which draw their nutriment from living cells 
by haustoria (endocellular haustorial parasitism), e.g. Peronospora, Cystopus. 
(c) Diseases affecting only live epidermal cells (epidermitis), e.g. Erysiphales. 
(d) Diseases in which the parasite grows between the living host-cells ; ab- 
sorption is by the intercellular mycelium (intercellular mycosis), e.g. rusts. 
(e) Diseases in which the host tissue is displaced or replaced by fungous 
masses (mycosclerosis), e.g. Claviceps and the smuts. 
(/) The tumor-like diseases, e.g. Pseudomonas tumefaciens. 
III. The parasite living within host-cells or tissues which have recently been 
killed or partly disorganized by it : 
(a) Diseases in which the dominant feature is death of the host-cells before 
they are actually invaded by the parasite (necrosis). According to the part 
involved we may recognize : 
{i) Cortical necrosis, in which the cortex chiefly is involved, e.g. Sphaeropsis* 
(ii) Parenchymal necrosis, in which the parenchyma, including the greater 
number of the soft rots, is affected, e.g. Rhizopus, Penicillium. 
(Hi) Macular necrosis, in which necrosis is limited to spots chiefly occurring 
on leaves. Of this there are two types, according to whether there is 
abscission or not. Examples of the former are Cylindrosporium and 
Marssonia ; if the latter, Pscudopeziza and Septoria. — R. J. L, ^ j 
Plant Peroxidases, The Supposed Action of Potassium Permanganate with. 
By H. B. Bunzell and H. Hasselbring (Bot. Gaz. vol. lxiii. No. 3, March 191 7, 
pp. 225-228). — In the Bot. Gaz. vol. lxii. pp. 233-238, Reed describes experi- 
ments which he carried out, which led him to conclude that in oxidation processes 
catalyzed by peroxidases two reactions are involved : first, a combination of the 
peroxidase with oxygen from substances acting as oxygenases ; and second, 
a transfer of this oxygen to the substance oxidized by means of peroxidases. 
In this way he believes that the mechanism of oxidation in living tissues could 
be accounted for. As the result of the investigations of the present writer 
it seems that in the reduction of potassium permanganate by organic substances 
in neutral solutions hydrated peroxides of manganese are formed, which are 
held in solution and which, though they are reductive products of permanganic 
acid, are still capable of carrying out oxidations. It appears extremely probable 
that the oxidation phenomena observed by Reed were brought about by such 
peroxides of manganese and not by activated plant peroxidases. Moreover, 
since a number of substances acting on potassium permanganate give mixtures 
which oxidize other compounds, there is no evidence in Reed's experiments 
that the reduction of the potassium permanganate was brought about by plant 
peroxidases. — R, J. L» 
Plants and the Winter. Anon. (Irish Gard. xii.pp. 136-141, Sept. 1917). — 
Very interesting reports containing lists of plants which were killed, injured, 
or remained uninjured after the severe winter of 191 6. — E. T. E. 
Polyporus Schweinitzii. By J. M. Murray (Trans. Roy. Scot. Arb. Soc. vol. xxx. 
PP- 5 6_ 57> January 1916). — This fungus has been known on the Continent lor 
many years as an enemy of Scots pine, Weymouth pine, and larch, but has not 
been considered a serious enemy. In the United States it is common through- 
