270 Sargent . — Notes on the Life- History of Pterostylis . 
about 40, in P. Sargenti about 35, in P. vittata about 2 hours, and in 
P. recurva about 3 hours, during the warmer hours of the day. These 
times are usually doubled before 10 a.m. and after 4 p.m., and throughout 
dull days. There are many variations ; but good healthy specimens can 
generally be relied upon to keep pretty close to the times I have given. 
Perhaps departures from the usual time are always evidence of something 
wrong. The same specimen, however, often varies its time a little from day 
to day. 
Time being up, the labellum returns to the c ready 5 position sometimes 
abruptly, sometimes by several short jerks, and sometimes with a continuous, 
slow, even motion. Even the same labellum behaves differently in this 
respect on different occasions. 
The appendage is not immediately sensitive to touch, when the labellum 
has reached the ‘ ready ’ position. Irritability is regained after a lapse of 
time, varying in different species from a few minutes to half an hour. 
The labellum is insensitive, I believe, all the while that the flower is closed. 
Tickling the appendage with a bristle while in that position seems to 
have no effect on the duration of closure. 
Let us now leave mechanical details and examine the plants ‘ at home ’. 
In my experience they are almost always found in shady situations, under 
bushes or amongst rocks. The flowers are remarkably inconspicuous in 
their natural surroundings (PI. XVIII). Being mostly greenish-white with 
green longitudinal markings, or bands, they appear green. P . reflexa is 
rufous, and P. rufa> I believe, is usually so, though most of the specimens 
I have collected are green. P. vittata occurs in two forms, green, and deep 
reddish brown. P. reflexa blooms early in the season, and its rufous blossom 
is not readily seen against the background of dull brown earth and yellowish 
dead vegetation. Even its later flowers amongst green grass must be looked 
for to be seen. The flower of P. constricta is green ; and when the plant grows 
amongst grass, it is decidedly difficult to see. P. Sargenti has a deep green 
flower, easily overlooked as the plant usually grows in dark coloured soil. 
P. recurva and P. turfosa are well hidden by the tangle of bushes, amongst 
which they occur. My experience of P. rufa is that the grey-green flowers 
harmonize so well with the green-grey granite inhabited by the plant, that 
I have often looked hard at a specimen for several minutes before seeing it. 
To this lack of conspicuousness add the facts that the flower is odour- 
less and devoid of nectar, and take into consideration the irritability of the 
labellum ; and the conclusion that the flower is nothing but a trap is almost 
inevitable. But that is not all, there are other things to be reckoned with. 
I have often found the flowers of P. vittata and P. Sargenti with their 
labella missing. It seemed they had been gnawed off. This points to there 
being something attractive about the labellum. The behaviour of the 
diptera, which visit the flowers, strengthens this idea. I have seen these 
