THE MONOCOTYLEDONES 21 15 



Finally, wc may refer to the flower structure in the genus Catasetum 

 (Fig. 2054). It is an American genus of about forty species. The plants 

 live as epiphytes in the tropical rain forest. The flowers are extremely 

 diverse in form, so difl"erent in fact that were they not sometimes found in 

 the same inflorescence, they would undoubtedly be placed in different 

 genera as indeed they originally were. These different forms are moreover 

 usually of different sex (Fig. 2054). In the predominantly male flowers of 

 C. saccatum the upper sepal and two upper petals surround and protect 

 the column, the two lower sepals project outwards at right angles. The 

 flower is more or less inclined, with the labellum hanging downwards. 

 In front of the column lies the deep stigmatic chamber and lying above it is 

 the viscid disc. Though termed a stigmatic chamber it is completely sterile 

 and incapable of receiving pollen. Moreover the disc, though of great size, 

 is so placed that it could never come into contact with an insect. Instead, 

 the rostellum is prolonged into a pair of curved tapering horns, referred to 

 as the antennae, which are extremely sensitive. No nectar is secreted but 

 the flowers are conspicuously marked. An insect flying to the flower is 

 almost certain to come into contact with one of these antennae. Should 

 this happen a stimulus is produced which causes the anther covering to 

 split and the pollinia are immediately forcibly ejected a distance easily 

 sufficient for them to become stuck on the insect by their adhesive points. 

 For long these flowers were regarded as exclusively male and the female 

 flowers were not recognized, though actually they were known under a 

 separate genus Monachaiithus. The flower is of very different appearance 

 from the male; the pollen sacs are rudimentary and never open, while the 

 antennae are absent. On the other hand the labellum is not as large and 

 the other perianth segments are reflexed. Instead of a large stigmatic 

 cavity there is a narrow cleft beneath the anther just large enough to receive 

 a single pollinium. In addition to these two types, a third has been recog- 

 nized in which both sexes are represented. This used to be referred to a 

 genus Myanthus. It preserves the general form of the male flower so far as 

 the petals and sepals are concerned but the labellum more closely resembles 

 that of the female. Two antennae are present though not as long as those 

 in the male. The stigmatic chamber is of medium size, intermediate between 

 the large one of the male and the small one in the female. Unfortunately 

 no modern work on the pollination of this genus appears to have been done 

 and this description is based upon that of Darwin who was still not wholly 

 satisfied that he was dealing with three forms of the same flower. 



Space will not allow us to consider the many and interesting genera 

 which are in cultivation. Among the more important, however, we may 

 mention Odontoglossum (Figs. 2055 and 2056), a genus of 100 epiphytic 

 species occurring in the mountains of tropical America; Maxillana (I-ig. 

 2057), with no tropical species; Vanda (Fig. 2058), with twenty-five Indo- 

 Malayan epiphytes; and Cymbidium, with about forty species in Africa and 

 Asia, including Japan. 



Possibly there is no more remarkable group of flowermg plants, cer- 



