248 BOTANY. 
from the top; but once inside, it finds it difficult to escape 
by that route on account of the incurved margins of the 
opening, as well as the smooth sides of the slipper. It ac- 
cordingly passes backward under the dependent stigma, 
and escapes by squeezing between the column and base of 
the slipper: in doing this it covers its back with sticky 
pollen from the anther on the column. When it visits 
another flower this experience is repeated; and as it passes 
under the stigma in its endeavor to find an exit, some of 
the pollen is left on its surface. 
522. Among the tropical Orchids there are some marvel- 
lous flowers. One of the most remarkable of these is a 
large flowered species of Catasetum, native of South 
America. The flowers are diclinous, i.e., the pollen and 
the ovules are produced in different flowers. The column 
of the staminate flower is furnished with a pair of slender 
horns, one or both of which are sensitive. The pollen- 
masses are curved and in a state of tension, like a curved 
whalebone spring. Now, when an insect alights on the lip 
of the flower and comes in contact with one of the sensitive 
horns, the pollen-mass is instantly set free with a jerk suf- 
ficient to throw it nearly a metre, and in such a direction 
as to strike and adhere to the head of the insect. When 
the insect visits a pistillate flower, the pollen-mass is in the 
proper position to be brought in contact with the stigma, 
thus effecting pollination. 
528. Much might be written about these truly wonderful 
plants, but what has been said must suffice to call the at- 
tention of the student to them. Our native species will 
well repay a careful examination, while the exotic ones, of 
which hundreds are now grown in conservatories, show a 
greater variety. in form and color of flower than can be 
