74 | THE ORCHID REVIEW. (May-JUNg, 1919, 
“Certain species would appear.to be almost drought proof. Until quite 
recently I believed that a ten-inch annual rainfall provided the: minimum 
amount of moisture necessary for the maintenance of Orchidshere. There 
would, however, appear to be at least one exception. Quite recently I 
received Pterostylis rufa from outside this line of rainfall, in our central 
desert country. Now the genus Pterostylis is generally a shade and moisture- 
loving one, P. rufa being exceptional in that it is a summer form, blooming 
in tne very hot weather (November and December). I knew that it pene- 
trated very far north, but would a fortiori have excepted some of the more 
hairy forms of Caladenia as more likely to survive in that country than 
any Pterostylis with which I was acquainted. The following facts, however, 
are interesting in this connection. The tubers of Pterostylis rufa are un- 
usually large in comparison with the size of the plant, and its power of 
resisting dessication is most remarkable. I may add that it is quite naked 
and unprotected by scales. On one occasion I found a plant of it growing 
in the cleft ot a rock in the middle of a stream, and brought home the tuber, 
intending to plant it, placing it on a small mantlepiece, where I saw it from 
time to time, but for various reasons neglected to carry out my intentions. 
In the following season I was surprised to find that it. was beginning to 
vegetate. During the whole of this time it had not received any moisture 
other than that it could obtain from the bare marble slab; the summer had 
been very hot (sometimes over 100° F.), and the atmosphere exceedingly dry. 
I watched it. It threw up the usual rosette of leaves, then a scape and bud. 
My wife at this point in its history, unfortunately, took pity on it and potted 
it, when a slug promptly ate it and brought my observations to a close. 
_ The endurance and vitality of this plant under such drastic conditions are 
however worth recording. 
_ “ Among Australian terrestrial Orchids natural hybridisation undoubtedly 
occurs, and has to receive careful consideration. when dealing with any 
supposed new species. I have observed it chiefly in Diuris, Thelymitra, 
Prasophyllum, Microtis, Pterostylis, and certain species of Caladenia. Such 
hybrids, howeyer, do not appear to be presistent, for in several instances I 
have marked the localities, but they have failed to reappear in subsequent 
seasons. They often occur in places which are under constant observation, 
such as our National Park, where the Orchidaceous flora is thoroughly known. 
On looking over my collection of drawings I notice one of a hybrid which I 
suspect to be Diuris longifolia x D. pedunculata, and I am sending you a 
copy of it.” 
It would be interesting to have particulars of the conditions under which 
this Diuris was found. Presumably it came from a locality in which the’ 
two Supposed parents grow together, for its characters are fairly inter- 
mediate, as is. apparent on comparison with coloured figures of the latter. 
