142 
nutritious juices of the plant. It also occurs abundantly on the wild 
verbena plants native in our own region, and often conspicuously re¬ 
duces their usual vigorous appearance. 
The term black rust is distinctively applied to a peculiar discol¬ 
oration and enfeeblement of the youngest, terminal part of the stem 
and youngest leaves. Most of these parts assume a dark purplish 
color, but sometimes a sickly yellow instead. The changed color is 
not due to the death of the leaves or their parts, as in the other 
case, but occurs while growth is still in progress. With the effects 
of mildew the plants are more disposed to grow slender and weak, 
but tall; where attacked by the black rust, however, terminal growth 
is retarded, and flowering is almost wholly prevented. This latter 
disease is only known on the cultivated plants, and as far as ob¬ 
served by the writer, only on the verbena, although something of 
similar appearance occurs on others. 
The agent is a mite which works on the surfaces affected, where 
also it deposits its eggs and completes its development. When the 
plants are removed from the house to the open grounds the enemy 
accompanies them and lives upon them during the summer, to he 
transferred very often again to the house, with the cuttings from 
which propagation is practiced. Much injury and consequent dis¬ 
satisfaction occur. The living, crawling animal, with its sharp 
mouth-parts, is much too small to be seen by the unaided eye on 
the plants, and even with a good hand magnifier it requires good 
handling, and perhaps special practice, to readily make them out. 
But an affected leaf, under a compound microscope with an inch 
objective, may be found swarming with the mites in various stages 
of development. 
They are killed by hot water at a temperature of one hundred and 
twenty (120) degrees Fahr. The plants may be safely immersed in 
such water for a half minute, and as this is practicable with potted 
plants, a means of cure is accessible to all. It is also probable [( 
that an emulsion of coal oil will effectually destroy the mites with¬ 
out injury to the plants.” 
REMEDIES FOR MITE ATTACKS. 
The remedies usually employed for mite attacks are such as have | 
been found useful in destroying aphides. Sulphur applied in several 
ways and combinations is the remedy employed with most success. 
Simple flour of sulphur applied to the moist leaves is recommended 
by Townend Glover as a means of destroying the red spiders which 
cause rust on cotton. A mixture of soap, sulphur and water, and 
also soapsuds and quassia water, are others which may be found 
useful. Moisture, for some reason, is obnoxious to mites, and 
thorough and repeated drenchings of the infested leaves with pure 
water will be found sufficient in most cases to stop their depreda¬ 
tions. To be effective, other applications will need to be so thrown 
upon the under side of the leaves as to reach the mites, for some 
of them are very tenacious of life. I have kept Pliytopti floating on 
glycerine twenty-four hours, and found them, at the end of that 
time, apparently as active as when taken from the leaves. The 
gall-producing Phytopti cannot be treated as readily as those which 
