Chap. VII. CATASETUM TKIDENTATUM. 195 



brane formed of polygonal cells, resting on and adhering 

 to a thick cushion, formed of irregular rounded balls 

 of brown matter, separated from each other and em- 

 bedded in a transparent, structureless, highly elastic 

 substance. This cushion towards the posterior end of 

 the disc graduates into viscid matter, which when 

 consolidated is brown, translucent, and homogeneous. 

 Altogether the disc of Catasetum presents a much 

 more complex structure than in the other Vandeee. 



I need not further describe the present species, 

 except as to the position of the antennae. They oc- 

 cupied exactly the same position in all the many 

 flowers which were examined. Both lie curled within 

 the helmet-like labellum ; the left-hand one stands 

 higher up, with its inwardly bowed extremity in the 

 middle ; the right-hand antenna lies lower down and 

 crosses the whole base of the labellum, with the tip 

 just projecting beyond the left margin of the base of 

 the column. Both are sensitive, but apparently the 

 one which is coiled within the middle of the labellum 

 is the more sensitive of the two. From the position 

 of the petals and sepals, an insect visiting the flower 

 would almost certainly alight on the crest of the la- 

 bellum; and it could hardly gnaw any part of the 

 great cavity without touching one of the two antennae, 

 for the left-hand one guards the upper part, and the 

 right-hand one the lower part. When either of these 

 is touched the pollinium is ejected and the disc will 

 strike the head or thorax of the insect. 



The position of the antennae in this Catasetum may 

 be compared with that of a man with his left arm raised 

 and bent so that his hand stands in front of his chest, 

 and with his right arm crossing his body lower down 

 so that the fingers project just beyond his left side. 

 In Catasetum callosum both arms are held lower down 



