206 VANDE.E. Chap. VII. 



thorax. When the bee walks about, the pollen-mass 

 lies flat on the back and wings ; but when the insect 

 enters a female flower, always with the labellum turned 

 upwards, the pollinium, which is hinged to the gland 

 by elastic tissue, falls back by its own weight and rests 

 on the anterior face of the column. When the insect 

 returns backwards from the flower, the poUinia are 

 caught by the upper margin of the stigmatic cavity, 

 which projects a little beyond the face of the column ; 

 and if the gland be then detached from the back of 

 the insect, or the tissues which connect the poUinia 

 with the caudicle, or this with the gland, break, fecun- 

 dation takes place." Dr. Criiger sent me specimens 

 of the humble-bees which he caught gnawing the 

 labellum, and these consist of Euglossa nov. spec., ca- 

 jennensis and piliventris. 



Catasetvm mentosum and a Monachanthus, according 

 to Fritz Miiller,* grow in the same district of South 

 Brazil ; and he easily succeeded in fertilising the 

 latter with pollen from the former. The pollen-masses 

 could be inserted only partially into the narrow 

 stigmatic cleft ; but when this was done, a process of 

 deglutition, as described under Cirrhaea, commenced 

 and was slowly completed. On the other hand, Fritz 

 Miiller entirely failed in his attempts to fertilise the 

 flowers of this Catasetum with its own pollen or with 

 that from another plant. The pollinia of the female 

 Monachanthus are very small; the pollen-grains are 

 variable both in size and shape ; the anther never 

 opens, and the pollen-masses are not attached to 

 the caudicle. Nevertheless, when these rudimentary 

 pollen-mass^, which can never naturally be removed 

 from their cells, were placed on the slightly viscid 



* 'Bot. Zoitirag,' 1868, p. 630. 



