THE TWAY-BLADE— continued. 
two parallel strap-shaped lobes with a minute point between them. We have known 
this plant spoken of as the “ Green Man Orchis ” by those who, aware of the 
existence of a Man Orchis, were not acquainted with Aceras anthropophora Brown ; 
but, in spite of the Grecian sage’s definition of man as “ a two-legged animal 
without feathers,” arms are generally considered an essential part of a typical man, 
and Listera has no structures to represent arms, while Aceras has. Down the median 
line of the basal half of the labellum is a honey-secreting groove ; and, whether the 
flower has, as has been suggested, some scent which is imperceptible by us, or not, 
insect-visitors are frequent, small beetles and flies more especially. 
The column arches over the base of the labellum, having on its under side the 
two receptive stigmatic lobes and, between them, the flat leaf-like pointed rostellum. 
This is provided with a series of longitudinal tubes filled with a viscid milky fluid, 
and is most sensitively irritable, a touch by the thinnest human hair being sufficient 
to cause it to split across and exude some of the fluid. The two pollen-masses lie 
above the rostellum, protected by an arched hood-like termination of the column. 
They are each divided into two, but their retinacula are united, and the threads 
binding the grains together are so weak as to render the whole mass friable. 
The modus operandi of insect-pollination can be easily imitated with the point of 
a pin. Darwin describes how the visiting insect alighting on the lip of one of the 
lower flowers of the raceme crawls up it, eating the nectar in its median groove till 
it passes the sharp bend. It then inevitably strikes the over-arching, irritable 
rostellum, and two drops of the exuded fluid drag with them the united pollinia and 
glue them firmly and immediately to the insect’s head. The rostellum then curves 
suddenly downwards over the stigma to protect it from self-pollination and does 
not recover its position for some time. Thus this plant and Spiranthes are 
effectively protandrous. When the insect reaches flowers in the later stage at 
which the stigma is adhesive, the weakness of the threads binding together the 
pollen-grains permits a few of the massuU , or groups of pollen-grains, to be torn 
from the pollinia, which may thus serve to pollinate several flowers in succession. 
The seeds of Listera are noticeable, having the delicate transparent testa only a 
single cell in thickness, which is common among Orchids, drawn out into two long 
thread-like ends. 
The genus was named by Robert Brown in honour of Dr. Martin Lister 
(1638-1712), a correspondent of Ray and an excellent all-round naturalist, best 
known, perhaps, for his work in conchology and entomology. 
