276 General Notes. [March 
seven crystals, from almost every known locality in which this 
mineral is found. These results are embraced under fifteen heads. 
Under one of these he states that the electrical activity is greater 
in the green, brown, and red crystals than it is in black or color- 
less ones; and that the black crystals often show no electrical 
phenomena, but, on the other hand, are conductors of electricity. 
——The same subject has been treated in a paper by E. Riecke in 
the Annalen der Physik und Chemie. In his study of Brazilian 
topaz K. Mack? has found that-the electrical axis does not cor- 
respond to any crystallographic axis, and that in cases where the 
crystallographic axis does not exactly bisect the optical angle, 
this anomaly is accompanied by abnormal extinctions in the 
plane of the optical axes. 
BOTANY.: 
The Study of Plant Diseases.—Although the fungi them- 
selves have been studied in this country for many years, the dis- 
eases they produce have hitherto received little attention. One 
colleges and agricultural departments of colleges in the United 
usual thing to find professors teaching botany whose knowledge 
of the subject stops short of the.ability to handle the Compositæ. 
The Grasses and Sedges, to them, are little better than “ Crypto- 
gams,” and as to the latter, they are simply Cryptogams. From 
such botanists no study of plant diseases need be expected, 
Two recent publications ought to direct the attention of our 
botanists to this much-neglected field. Mr. Arthur's report, 
as botanist of the Agricultural Experiment Station at Geneva, 
N. Y., shows where and how good work may be done by those 
= 5 any 
the pages treating of the Pear Blight, and he cannot help feeling 
that the work there recorded is of a much higher order than that 
2 No. 5, 1886, p. 43... 2 Annalen der Physik und i Aa 
TaS PO ead E Eeay Ph nd Chemie, No. 6, 1886, p. 153 
P E 
kd 
