406 SYSTEMATIC BOTANY 



sepals, three petals, six stamens in two circles of 

 three each, and a three-celled ovary with three styles, 

 or a single style and three stigmatic points ; all the 

 circles alternating with each other, so that the stigmas 

 are opposite the sepals and alternate with the petals. 



In the Orchid, therefore, while the three sepals, 

 the three petals and the three-celled ovary are fully 

 developed, only one of the stamens is ; and the 

 solitary stigma must, since it faces the labellum, 

 really be the two front stigmas united into one. 

 Some or all of the remaining stamens may perhaps 

 be considered as making up part of the column, 

 with the undeveloped style as its central axis and 

 its stigma as the rostellum. The flower is usually 

 upside-down for the labellum, being the odd petal, 

 should point upwards but is brought to the lower 

 side by the twisting of the ovary. A similar twisting, 

 though more difficult to make out, occurs in the 

 Balsams (IMPATIENS). 



The differences between Orchid flowers are mainly 

 in the exact position of the anther-lobes, their attach- 

 ment, and the attachment of the polliniums to the 

 removable part of the column, technically known as 

 the rostellum. In the VANDA group the anther falls 

 off but the polliniums are attached by a strap to the 

 rostellum ; in the DENDROBIUM group the anther 

 is helmet-shaped and remains attached to a narrow 

 thread to the column (fig. 89) ; and in HABENARIA, 

 and Orchids like it, the anther lobes are separated and 

 attached firmly to the sides of the column. There is 

 another group, the Slipper-Orchids, CYPRIPEDIUM, in 

 which the structure is quite different, the flower having 



