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AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
III. Friday, July 28. The almost entirely dried branch was subjected 
for the third time to the air blast (from 10:00 A.M. to 12:00 M.). A micro- 
scopical examination on the same day (July 28) showed the presence of 
needle hairs in all preparations, but of only one club-shaped hair. 
At the end of experimental series i, a chloral-hydrate preparation was 
made of the entirely dried branch. The under side of the leaves, as is the 
case in the fresh leaf, were covered with many club-shaped and bristle-like 
hairs. 
B. Experimental Series 2 {July 2S-T,i, 1911). In this series of experiments 
a branch of densely haired R. Toxicodendron was used. A part was pressed 
and a chloral-hydrate preparation made of it. This showed a dense covering 
of both kinds of hairs. 
I. Friday, July 28. The experiment lasted from 12:30 to 2:30 P.M. 
On July 29, a microscopical examination disclosed a club-shaped hair in 
each of four preparations; the remainder showed many needle-shaped hairs. 
II. Saturday, July 29. The dried branch was blown on for two hours 
(from 1 1 : 00 A.M . to 1 : 00 P.M .) . A microscopical examination followed on 
Monday, July 30. This disclosed in 
Preparation i : Three club-shaped hairs, very many needle-shaped hairs, many dirt 
particles, and pollen grains of other plants. 
Preparation 2 : No club-shaped hairs. 
Preparation 3: Four club-shaped hairs, one with a piece of epidermis. 
Preparation 4: Two club-shaped hairs. 
Preparation 5: Two club-shaped hairs, one containing yellow protoplasm. 
Preparation 6: One club-shaped hair. 
Preparation 7 : Three club-shaped hairs. 
Preparation 8: No club-shaped hairs. 
III. Monday, July 31. The three-day-old branch was blown on from 
11:30 A.M. to 1:30 P.M. A microscopical examination on August I 
showed one club-shaped hair in each of four out of eight preparations. 
Both the glycerine-covered slides on the bottom of the case were free from 
club-shaped hairs. The cotton in the funnel contained no club-shaped 
hairs (the cotton having been soaked in glycerine and the excess pressed 
out). 
At the end of the experiment, a chloral-hydrate preparation was made 
from the three-day-old, entirely dried branch. Club-shaped hairs were 
present in abundance on the leaves. The club-shaped hairs could never 
wound the cuticle. 
Three further experiments were made, similarly to the first two, toward 
the end of August, in the second half of September, and soon after the 
middle of October, 191 1. The results were similar. In the first days none, 
or at most one or two, club-shaped hairs could be found in 8 to 10 prepara- 
tions. In the experiments with the twigs dried two or three days, only a 
few club-shaped hairs were blown loose. In many experiments in which 
