416 Scientific Intelligence. 
with great caution. In the volume now before us, the more 
difficulties, upon the consideration of which we cannot now enter, 
except to say they mostly spring from the transfer to such simple 
classification of plant-diseases proposed by Frank is plain and_ 
reasonably comprehensive. Four groups are made, viz: 
Effects of injurious mechanical influences, as distortions through 
lack of room for growth, and the many forms of wounds. 2. 
diseases induced by inorganic nature, such as come from too 
them rather than with their morphology. He speaks of three 
general effects produced by these parasite 1. a consumption of 
the living matter and its stored food. 2. Destruction of tissues 
3. Irritation inducing abnormal growth ughout 
is painstaking, which makes it of great utility as a wor 
reference, the citations being given with extraordinary accuracy. 
: G. I 
Researches on the Structure of Diatomacew, from the 
d 
a 
excellent plates, and also facts of geological farereat connected — 
with them. The diatoms are filled usually with calcite, but 
contain sometimes minute erystallizations of pyrite inside or as 
a coating; and the pyrite occurs commonly in the parts of the 
diatom (the perforations, especially) where the organic matter 
existed, to provoke the chemical reaction necessary for its pre 
cipitation. The author discusses also the origin of the pseudo- 
- 
