THE ORCHIDS OF NEW ENGLAND. 83 



developed. The lowermost division (lowermost in the accom- 

 panying figure), and the two upper ones form the lower series 

 or verticil, or, as it would be called in other orders, the calyx. 

 The lower leaf (lower as before noted), if the 3 were drawn 

 out on a stem as real green leaves, would be the upper or 3d in 

 the cycle, and we see that it has begun to change its form. The 

 next drawing in of the spiral twist, which has resulted in 

 another cycle or verticil of 3 leaves brought down to one 

 plane, has ended by bringing the upper normal leaf, and the 

 most changeable, as we have already seen, just opposite to 

 where the twisting of the lower verticil ended. ... In 

 other Orchids . . . another twist takes place in the 

 ovarium just as the petals are about to open and after all the 

 twisting so far described has been done, and the result is that 

 the lip (which in our flower is the uppermost leaf of the 2d 

 verticil) assumes the position of the lowermost part of the 

 * flower. In Calopogon the extra twist has not occurred, and the 

 result of this limited torsion is that the lip forms the upper 

 instead of the lower part of the flower." 



Some Orchids have the foot-stalk twisted instead of the 

 ovarium, Darwin says. In either case, " from slow changes in 

 the form or position of the petals, or from new sorts of insects 

 visiting the flowers, it might be advantageous to the plant that 

 the labellum should resume its normal position on the upper 

 side of the flower, as is actually the case with Malaxis paludosa 

 and some species of Catasetum, etc. This change . . . might 

 be simply effected by the continued selection of varieties 

 which had their ovaria less and less twisted ; but if the plant 

 only afforded varieties with the ovarium more twisted, the 

 same end could be attained by the selection of such variations, 

 until the flower was turned completely round on its axis." 

 Thus in Malaxis paludosa, " the labellum has acquired its pres- 

 ent upward position by the ovarium being twisted twice as 

 much as usual." 



