THE FLOWER 239 
gamic. They are much more prolific than ordinary flowers, 
but are not common, and seem to be a provision against 
accident, for the plants producing them are generally pro- 
vided with other flowers of the usual kind, —some, as the 
violet, having elaborate special adaptations for cross fertili- 
zation. 
y 
Practical Questions 
1. Why does a strawberry bed sometimes fail to fruit well, aiiours it 
may flower abundantly? (267, 268.) 
2. Are berries found on all sassafras trees? On all buckthorns? 
Hollies ? 
3. Would a solitary hop-vine produce fruit? A solitary ash hee? ig 
(267.) ‘ 
4, Why is a mistletoe bough with berries on it so iniiele harder to find 
than one with foliage merely? (267, 268.) 
B. Winp PoLiinatTion 
Marertat. — In spring, catkins of forest trees, staminate and pistillate 
flowers of pine. At nearly all seasons, heads of grain and panicles of va- 
rious kinds of grass can be obtained. For experiment, a potted plant of 
any kind, just about to bloom, may be used. 
ExpErRiment 80. To TEST THE EFFECT OF SHUTTING OUT EXTERNAL 
AGENCIES. — Tie paper bags over flower buds of different kinds when nearly 
ready to open and leave until the flowers have withered. On removing 
the bags, mark with colored threads the flowers that had been covered, and 
watch until seed time. Do you notice any difference in the number, size, 
or weight of the seed produced by them and by those of the same kind left 
exposed? How do you account for the difference, if there is any? By 
what agencies could foreign pollen have been carried to the stigmas of 
the exposed flowers? If any of the covered specimens wither and drop 
their seed vessels without any attempt to fruit, examine a fresh flower, and 
see if it is capable of self-pollination. 
As already explained, experiments of this kind, to be conclusive, should 
be tried on as many specimens as possible. The greater the number of 
species and individuals included, the better. Where it is not practicable 
to carry on experiments by the class, pupils who are interested can make 
them at home. 
273. The problem of pollination. — When a plant has pro- 
vided against self-pollination, its problem is only half solved, 
