246 PRACTICAL COURSE IN BOTANY 
ment by turning the pot bottom upwards so that the flowering axis will 
point downwards. This can be done by inclosing the pot in a bag of strong 
cheesecloth, with the string tied loosely but firmly around the foot of the 
stem to prevent the contents from falling out, and suspending the whole 
bottom upwards. In making these experiments, use flowers that grow 
in a long cluster, or raceme, and hold the main axis in a vertical position 
by tying or weighting it down. Watch the behavior of the individual 
flowers. Arrange another pot containing the same kind of plant, in the 
: same way, and suspend one 
in a dark place, keeping the 
other in the light. Does the 
same movement take place in 
both? Is it in response to 
light, or to gravity? 
280. Means of pro- 
Fies. 360, 361. — Protection of pollen in the tection. — Where plants 
thistle: 360, position at night, or during wet have adapted them- 
weather ; 361, position in sunshine. selves to insect polli- 
nation, it is, of course, important to shut out intruders that 
would not make good carriers. In general, small, creeping 
things, like ants and 
plant lice, are not such 
efficient pollen bearers 
as winged insects, and 
hence the various de- 
vices, such as hairs, 
scales, and constric- 
tions, at the throat of 
the corolla, by means 
of which their access to 
the pollenis prohibited. 
To this class of adapta- 
tions belong the hairy 
filaments of the spider- , 
‘ ‘ Fics. 362, 363.— A bell flower: 362, position 
wor t, the sticky TING ig daylight; 363, position at night, or during wet 
about the peduncles of weather 
the catchfly, the swollen lips of the snapdragon, the scales or 
hairs in the throat of the hound’s-tongue, the velvet petals 
362 363 
