216 MR. HENRY RIDLEY ON ORCHIDEX AND 
bium crumenatum, Sw., is the best known, invariably produce 
their flowers simultaneously on certain days. The special day 
holds good throughout the district; almost every plant bursts 
into blossom, and may remain in flower for but a few hours, 
sometimes a whole day ; after which the flowers wither and no 
more appear till the next flowering day. Even plants brought 
from as far north as Siam to Singapore conform immediately 
to the Singapore day, and do not flower on that of their native 
place. Observation seems to show no correlation with the 
weather; though if there is very heavy rain on the day that 
the flowers are ready to open, they usually delay till it is 
over. Besides Dendrobium crumenatum, Sw., D. teres, Lindl., 
D. Kunstlert, Hook. f., D. criniferum, Lindl., and other species 
of the Desmotrichum section of Dendrobium, Bulbophyllum 
concinnum, Hook. f., B. macranthum, Lindl., Eria floribunda, 
Lindl., E. densa, mihi, &c., behave in the same way. The 
advantages for purposes of fertilization, especially in the case 
of plants producing flowers singly, is obvious; for were these 
to flower one at a time, as their blossoms are but short-lived, 
they would run a great risk of not being fertilized at all. But 
what causes the plants to break out into bloom on a definite day 
is not at all clear. 
There is a considerable variation in the method of opening 
of the flowers. 
In some, all the flowers in the raceme open simultaneously, 
as in Cirrhopetalum. Others produce a raceme which, growing 
and elongating slowly, bears each day three or four fully open 
flowers only; these, unless fertilized, fall the next day, before 
or as soon as the next three or four open. A raceme of 
Grammatophyllum, developing in this manner, will last for a 
month and a half. The intervals of time between the opening 
of the two adjacent flowers may be thus from one to several 
days; but they are longest in the Fornicarie, Thrizsperma, and 
Bulbophylla of the section Intervallate. Here the rhachis grows 
very slowly, and the flowers open one by one, with intervals of 
from about 10 days (Dendrocolla filiformis, Ridl.) to more than a 
month (Bulbophyllum Stella, Ridl.) ; so that a raceme may take 
nearly a year before it has come to the last flower. 
Distribution. — The orchid- flora of the whole region is 
tolerably homogeneous, and may be generally spoken of as 
strictly Malayan; a considerable proportion being common to 
