BOTANICAL GAZETTE. 427 
mold abstracts much of this and promptly sets it free by transpiration; and 
hen a piece of bread nearly as large as the mouth of the glass is used, the 
transpired water is so copious that it soon collects on the sides of the glass, 
appearing first as a faint mistiness, then as drops. Even before the moisture 
is visible, the plants show a marked sensitiveness to its presence, the tufts of 
fertile threads standing out at right angles to the damp surface. When the 
inverted bottom of the tumbler is reached, the same repellent action is evident, 
the tufts being pendent, while the few which develop in the angl d the 
then a cluster o rangi rom xact 
edge of the piece of bread, when it makes equal angles with the side and to 
e, representing a few many cases 0 a single cul- 
heliotropism and hydrotropism are so much stronger than geotropism in this 
common mold that they are very easily demonstrated to a class by it. 
Wa. TRELEASE. 
Cultivation of Pollen-spores.— In the cultivation of pollen-spores those 
of monocotyledons are most responsive, and of all that have been tried those of 
radescantia are the most serviceable. The pollen tube begins to develop in a 
constructed of blotting-paper or card-board, as suggested by Bower and Vines 
in their Practical Botany, p. 16, and by Goodale in his Physiological Botany, 
: The points which experience with this special plant suggests are: 
1. The culture drop, for a quick response, should be a saturated solution 
ture drop added. If the spores are sown on the culture drop they will remain 
too far removed from the objective, and the tubes will mostly grow towards he 
objective and so be seen in optical section instead of in profile. 
Spores should be obtained from flowers that have been open for some 
e, 
Tradescantia is so common, the moist chambers are so simple, and the re- 
Sponse so immediate, that it would seem a pity for any student to fail seeing the 
extine ruptured and the intine developing into a polien tu M. C. 
A Cheap Dissecting Microscope.—No laboratory oF workers need be un- 
supplied with dissecting microscopes. If even the cheapest form m — 
by the Opticians is beyond the means of the school or individual, an e ective 
stand may be made as follows: Into any block of wood of suitable size fix up- 
surf h ) 
the center, so that the cork will 
ne end of the smaller wire into suitable 
to hold whatever lens is at hand, ) — 
cork at right-angles to the first. arrangement gives ample 
creme ‘ ve) - vg any direction for adjustmen he plan oy fects 
* to any desired extent. If ge per re pie ak Ph f black 
be done on a piece aid fla : ; 
* white paper siadaonaatle will give the backgrounds gainst — any pat 
see r dissecting in liquid a d re. individual are P groin is 
hen “’ ires some transmitted light the object sa ty, Sloping blocks 
om of an inveried tumbler which has @ : os 
ill better illumination may 
Sti md 8% 
(sot 
os ie ot : : es Nr ha. gem. 
| Ae. ; i Ji2. 
