THE MOXOCOTYLEDONES 



2113 



Fig. 2052. — Catthya maxima. A, Flower. B, Lateral, sectional view of 

 flower showing the column enclosed by the labellum. One anther 

 cell is cut open and shows a pollinium with caudicle attached to the 

 rostellum, below which is the stigma and the canal leading to the 

 ovar>' cavity. C, Column as seen from below. (A after Bateman. 

 B and C after Dane in.) ^ 



kept closed by a spring at its point of attachment on the top of the column. 

 An insect visiting the flower may not, in the first instance, touch the 

 rostellum, but during its retreat from the flower is almost certain to cause 

 the exudation of a viscid fluid from the rostellum and bring out the pollinia 

 on its head. In one species in Trinidad it has been observed that the flowers 

 rarely open, though they produce fertile capsules. In this case the pollen 

 apparently germinates in situ, the pollen tubes growing directly down into 

 the ovary. A similar condition has been described occasionally in Eptden- 

 drum, a large genus with about 400 species occurring in tropical America. 

 Like Cattleya many species of Epidendrum are in cultivation. 



The genus Calanthe contains about 120 tropical species and is interestmg 

 because about eight pollinia are produced. Darwin studied the case of 

 C. mastica (Fig. 2053). Two stigmas are produced as oval pit-like structures 

 lying on either side of the rostellum. There is an oval viscid disc to which 

 are attached eight stalked pollinia which are covered at first by the anther 

 membrane. The labellum is united almost completely to the column leavmg 

 a passage to a nectary lying beneath the rostellum. If an insect enters the 

 flower it withdraws on its head the viscid disc with the eight pollinia 

 attached to it which spread out like a fan. They undergo no change in 

 position once they are withdrawn but when the insect thrusts its head into 

 another flower the pollinia are laterally compressed and strike upon the 

 stigmatic surfaces which, as we have seen, lie on either side of the rostellum. 



