I20 NATIVE BRITISH ORCHIDACE^ 



Paul Rohrbach (Prize Essay on Bpipogium Gmelwi, 1866) saw it twice visited by 

 Bombus Iticorum, which alighted on the thick rounded end of the inverted spur, and 

 crawled over the adjoining tip of the Hp, and down its deeply channelled centre to 

 its base, guided by the coloured ridges on each side, and by the spots within the spur 

 (honey-guides). There the lip turns sharply upwards, and the bee on rounding the 

 bend finds itself at the mouth of the spur, and can bore through the tender inner wall, 

 and suck the sweet juice. On retreating from the flower it crawls down the column, 

 and its head comes into contact with the rostellum, the tender skin of which bursts 

 at the slightest touch. The very adhesive matter gushes out, and attaches the viscidium, 

 to which the ends of the caudicles are affixed,^ to the forehead of the insect, so that 

 the poUinia are thus withdrawn. These would be liable to damage by scraping from 

 the pressure of the anther, were it not for a projecting point on the front of the latter, 

 so arranged that the bee pushes against it on leaving, pressing down the anther, and 

 giving free passage for the easy withdrawal of the poUinia. A similar provision is 

 made in Epipactis palustris, from which the pollinia are not cleanly withdrawn unless 

 the apex of the anther is pressed upwards, which is automatically done by the bee 

 on quitting the flower. 



Occasionally only one pollinium is withdrawn, but as it contains enough pollen 

 to fertilise a number of flowers, no great harm is done. The viscidium with its 

 ribbon-like caudicles is attached to the bee between the eyes, and the weight of the 

 pollinia makes these lie flat on its head, so that the pollinia project forwards like a 

 pair of club-shaped antenna. When the bee visits another flower, and pushes his 

 head upwards to reach the nectar, the pollinia come in contact with the projecting 

 stigma, the viscid material of wliich is sufficiently adhesive to detach a certain quantity 

 of pollen, by breaking the slender tlireads by which they are fastened to the pollinia. 

 Incidentally it may be mentioned that the lip, if displaced, springs back to its original 

 position near the column. But for this, a humble-bee, pushing his way in, might so 

 widen the space between lip and column that the next visitor carrying pollinia would 

 fail to deposit any of his precious burden on the stigma. 



Epipogon is one of the most extraordinary of terrestrial orcliids. It affords a com- 

 bination of characters peculiar to such widely different tribes that it is hard to say 

 what its natural affinities are. Its rootless rhizome and leafless stem resemble those 

 of Corallorhixa (Malaxideje), but the pollinia are like those of the highly evolved 

 Ophrydes. It thus combines a character of the Basitonas with those of the Acrotonas, 

 and the basal origin of the caudicles also is related to the former of these two great 



I Rohrbach CBlutenbau md Befruchtungvon Epipogium, p. 10) states that very seldom do the caudicles 

 faU to become attached to the viscidium which usually emits a little viscid matter which fastens them 

 to it so that they appear to be covered with a thin white membrane. If they remain free, one or both 

 become attached to the insect by the bursting of the tender skin on being touched and the outflow 

 of the viscid matter. Rohrbach's Prize Essay with two plates is worthy of study. 



