

















3, 1923] 
fossil organisms. It is pointed out that areas of 
bogland (Sumpfflachmoor) and peat may arise even 
in tropical conditions, moisture and low-lying land 
being the real necessities, and Wegener is cited as 
egarding all the great coal-basins as formed in a 
one of equatorial rains, The important question of 
annual rings in wood, discussed recently in Deecke’s 
*Palaophytologie"’ (see NaturE, September 16, 
P- 375), receives careful consideration, and the author 
concludes that these rings cannot be used by them- 
Selves as elucidating climatic conditions. Dr. Eckardt 
supports the view that seasonal changes of tempera- 
e have been felt in polar regions even when the 
climate was warmer over the whole earth; but at 
certain periods mild subpolar winters have been 
associated with summers much hotter than those 
of the present day. 
A. Handlirsch is interestingly quoted as showing 
how the length of the anterior wing in insects may 
be used as an indication of prevalent temperature, 
Since it increases at the present day from an average 
of 7 mm. in central Europe to 16 mm. in the tropics. 
he length in Lower and Middle Carboniferous strata 
in our latitudes is as much as 51 mm., but decreases 
in Upper Carboniferous and Permian times to 20 or 
to 17 mm. Little that bears on his subject has 
escaped Dr. Eckardt, and the correlation of scattered 
Scientific observations, in the hope of solving problems, 
is aptly illustrated in his concluding sentence, where 
he quotes Eckholm as showing that great importance 
‘must be attached to the obliquity of the ecliptic in 
NATURE 

395 
explaining the post-Glacial distribution of the hazel- 
nut in Scandinavia. 
Dr. Eckardt points out that at the present day 
the relative distribution of land and water has an 
influence on climate only about a third or a quarter 
as important as that of latitude. Prof. E. W. Berry, 
however, in a paper on a possible explanation of 
Upper Eocene climates (Proc. Amer. Phil. Soc., 
vol. 61, p. 1, 1922), urges that a prevalence of low- 
lying land as against mountain areas, and an enlarge- 
ment of oceanic areas, allowing of free circulation 
from broad equatorial basins to the poles, was a 
sufficing cause of the warmer, though still zonal, 
conditions revealed by Eocene vegetable remains. 
The Upper Eocene hazel, for example, came no 
farther south in Eocene times than lat. 45°, because 
the Atlantic basin resembled in breadth that of the 
present Pacific Ocean. The author even looks back 
to the views of Lyell, and suggests that ‘‘ the dis- 
tribution and altitude of the land and sea” may 
have accounted for the glacial epochs. 
A. Brockmann-Jerosch, who is much quoted by 
Dr. Eckardt, has recently suggested that glacial 
conditions in Switzerland were favoured by an 
oceanic climate and a copious rainfall (‘‘ Die Vegeta- 
tion des Diluviums in der Schweiz,’ Conférences 
de la Soc. Helvétique des Sci. nat., 1920, p. 73). 
Perhaps the proximity of the mountains in this area 
removed one of the factors relied on by Berry. 
There is clearly much philosophical discussion still 
before us in palzoclimatology. Gres C, 

















[NX the Mededeelingen v. d. Landbouwhoogeschool, 
; Wageningen, xxiv., No. 4, 1922, Miss de Bruyn 
publishes (in English with a Dutch summary) a paper 
entitled ‘‘ The saprophytic life of Phytophthora in 
the soil.” After reviewing the literature pertaining to 
fourteen species of the genus in relation to the ques- 
tion of their capacity for life as saprophytes in the 
soil, Miss de Bruyn describes her own work on the 
tivation of the three species, P. Syringe, P. 
throseptica and P. infestans, in soils of different 
pes. Most of the experiments were carriéd out 
with soil which had previously been sterilised, and 
details of the growth in this medium are given in 
Pach case. 
The general conclusion reached is that Phyto- 
phthoras are not such obligate parasites as was 
formerly supposed, and it is claimed that the experi- 
ments carried out prove that each of the species 
Mentioned can actually live and grow in the soil. 
ultures on sterilised soil as well as on other media 
vere exposed out of doors to rather severe frost for 
Several days, and it was found that P. Syringe and 
P. evythroseptica survived such treatment. So far 
the cultures in soil are concerned, however, it 
would appear that such survival may have been due 
to the presence of oospores. In the case of P. 
infestans (the oospores of which are still unknown in 
Nature) the results of exposure to similar conditions 
were not concordant, and the question as to whether 
this species can overwinter in the soil is regarded as 
unsolved. It was found, however, that when grow- 
ing on sterile raw potato slices, P. infestans sur- 
vived a temperature of —9° C., although at this 
low temperature the potato slices themselves were 
pipekenes. 
Attempts were made to cultivate P. Syringe and 
P. erythroseptica in non-sterilised soil, but the results 
NO. 2783, VOL. I11] 
Studies on Phytophthoras. 
do not appear to have been very satisfactory. It 
seems clear that further and more critical work will 
have to be carried out before it can be accepted as 
convincingly established that these two fungi are 
really capable of sustained growth and development 
in ordinary soil. No information is given as to 
whether P. infestans was found to live and grow in 
ordinary unsterilised soil; and speculation as to 
whether the survival of this fungus in the soil from 
season to season may account for primary outbreaks 
of potato blight seems therefore altogether premature. 
Another recent contribution to our knowledge of 
this fungus is contained in a doctorate thesis presented 
to the University of Utrecht by Miss M. P. Loéhnis, 
entitled ‘““Onderzoek over Phytophthora infestans 
(Mont.) de By. op de aardappelplant.”” (Wageningen, 
H. Veenman, 1922.) An account of pure culture 
work with various media is given ; immature oogonia 
and oospores were found twice in cultures on raw 
potato and Quaker Oat agar. 
Experiments on the manner in which infection 
of the potato occurs are described, and in discussing 
the question of the propagation of the blight from 
season to season it is recorded that on five occasions a 
diseased tuber was found before any infection of the 
foliage was apparent. It is suggested that the fungus 
may perhaps subsist in the soil, but this point is not 
yet regarded as definitely established. Other matters 
- dealt with are the influence of the stage of develop- 
ment of the plant on its susceptibility to infection, 
the mode of entry into the tubers and growth of the 
fungus in the subterranean parts of the plant, the 
formation of wound cork and varietal resistance to 
blight. The thesis is provided with a summary in 
English, and a more detailed abstract of it will be found 
in the Review of Applied Mycology, 1. 8. Aug. 1922, 
P. 253- 
