226 THE ORCHID REVIEW. [AuGuST, 1912. 
a shield-shaped staminode, occupying a definite position with respect to the 
lip, the anthers shortened, and the pollen grains cohering into two sticky 
masses, situated just over two lateral openings of the lip; all these being 
adaptations to fertilisation by bees, as already described. The tribe 
Cypripediez contains four genera, two of which have retained the three- 
celled ovary of Apostasiez, and, curiously enough, both are Tropical 
American, while the other two have become one-celled by the loss of the 
three partitions, one being tropical Asiatic, the other widely diffused through 
the northern hemisphere. Thus, with a unity of type, in the suborder 
Diandre we find a division into two well-marked tribes, with progressive 
modifications of structure, an extended geographical diffusion, and definite 
climatic adaptations. 
In the meantime another and more successful type of variation had 
arisen, probably from some early form which had lost the three-celled 
ovary. In this, five of the stamens were destined to play a subordinate 
part, one only remaining fertile, and that the median one of the outer 
whorl, homologous with the staminode of the Diandre. And with it arose. 
a totally new organ, the rostellum, modified from the third stigmatic lobe, 
on the opposite side of the flower, its function being to secrete some viscid 
matter causing the pollen grains to adhere to the insect visitor, and thus 
prevent their loss during its flight to another flower. Correllated with this 
development we find the early stages of the union of the pollen grains— 
which were to witness such an enormous development later on—and the 
confluence of the stamens and pistils into a rigid central column—all of 
them adaptations securing greater economy of the pollen grains by 
preventing waste. The anther is operculate, and the filament reduced to a 
mere hinge. Here, also, is found a use for the abortive stamens, three of 
which seem to have been suppressed in the Diandre, the other two in the 
Cypripediee uniting with the median petal to form a lip, while in the 
Apostasiez they were suppressed, the lip being undifferentiated. 
The union of the two lateral stamens of the outer whorl to form the lip 
has been continued throughout the Monandre, while the two corresponding 
stamens of the innet whorl have been variously developed on the sides of 
the column, opposite to the anther, as wings or teeth, as circumstances 
required, doubtless playing their part in keeping the anther in position 
and in guiding the visiting insects along the required path. The presence 
of the remaining stamen—the median one of the inner whorl—is generally 
to be sought among the crests of the lip. This type of structure has been 
progressively modified along divergent branches and constitutes the great 
suborder Monandre. 
In the earliest and simplest type of the Monandre, as in Pogonia, we 
find the pollen powdery, but examination shows them to be united in fours 
