APRIL, 1907.] THE ORCHID REVIEW. 123 
F, hybrid, E. X kewense, might arise through the dominant presence of 
both the purple and the yellow characters, but as there is not room for both 
to develop fully, the result is a mosaic of the two, which appears as a 
blend. 
If this interpretation is correct, the F, hybrids, raised from E. xX 
kewense selfed, should come out as follows: On the average, out of sixteen 
plants raised, nine should be salmon-coloured, like E. x kewense, three 
purple, like E. evectum, three yellow, like E. xanthinum, and one white— 
the white form representing the absence of both purple and yellow. 
It is of course possible that more than two pairs of unit characters are 
concerned in this cross, e.g., the colour of the crest may be a distinct unit, 
as it is in other plants. If three pairs of characters are concerned the result 
would be eight distinct forms in F;, in the ratio of 27: 9:9:9:3:3: 3:1. 
Experiment alone can determine the unit-characters concerned in these 
hybrids, and the results of Mr. Rolfe’s experiments with E. x kewense 
will be awaited with much interest by Mendelians, as well as by Orchidists 
generally. C. C. Hurst. 
DIURIS LONGIFOLIA. 
THIS is a very interesting and pretty terrestrial Orchid which has just 
flowered in the collection of J. Wilson Potter, Esq., of East Croydon, who- 
received it from Western Australia. ‘The species of Diuris are rare in culti- 
vation, and I do not know of another at the present time, though three 
are recorded in Nicholson’s Dictionary of Gardening, and two of these have 
been figured in the Botanical Magazine, D. maculata, Sm. (t. 3156), and D. 
alba, R. Br. (t. 6201). Both of them flowered at Kew. I do not find a 
record of D. longifolia having previously appeared in cultivation. It was 
originally described by R. Brown in 1810 (Prodr. Fl. Nov. Holl. p. 316), 
from a dried specimen collected by Menzies, and appears to be rather 
widely diffused, being recorded from various localities in Victoria, Tas- 
mania, South and West Australia. The Western plant was named by 
Lindley Diuris corymbosa (Swan Riv. Appx. p. 51); but is now considered 
synonymous with D. longifolia. In fact the Tasmanian form has been 
figured as D. corymbosa (Hook. f. Fl. Tasm. i. pif, t. 105, fig. B.). It 
is quite unlike any other Orchid in cultivation, but may be briefly described 
as a terrestrial plant, a foot or more high, with a few narrow radical 
leaves, and a scape of several moderate-sized yellow and purple flowers. 
The dorsal sepal is broadly ovate, and the lateral pair long and narrow (the 
generic name being being given in allusion to the two tails). The petals 
are spreading, and spathulate, while the lip is deeply three-lobed. The 
genus contains rather over a dozen species. 
An interesting note appeared in the Botanical Magazine when D. alba 
