NOVEMBER, 1916.] THE -ORCHID “REVIEW. 27% 
E =| ACIANTHUS _ SINCLAIRII. 
HE New Zealand terrestrial Orchids are very rarely seen in cultivation, 
but a specimen of the interesting little Acianthus Sinclairii, Hook. f., 
has been sent to Kew by H. J. Elwes, Esq., with the remark that it was 
grown by Mr. Burton, Longnor Park, Salop. It is an inconspicuous little 
plant, only a few inches high, bearing a single cordate leaf and a spike of 
small greenish flowers, which, according to Mr. Cheeseman (Trans. N. Zeal. 
Inst., vii. 349), are fertilised by small flies. He remarks: ‘‘On a warm 
sunny day it is almost impossible to watch a bed of this Orchid for any 
length of time without seeing numerous Diptera flitting from flower, 
busily engaged in robbing them of their sweets.” The flowers are thus 
fertilised, for on fourteen plants bearing 87 flowers seen in one locality no 
fewer than 71 matured capsules, while a set from another locality had 
borne 47 flowers, of which 44 had ripened capsules. And he adds that 
when the plant is covered up, or allowed to expand its flowers in a room, 
the pollinia remain in their cells and never reach the stigma, which shows 
that insect aid is required. He has several times seen insects remove the 
pollinia, and on one occasion saw a pollen-mass left on the stigma, and 
he remarks that under natural conditions the flowers are’so frequently 
visited that the pollinia are generally removed directly after the opening of 
the blossoms. 
The mechanism by which fertilisation is effected is described. The 
column arches over the broad, slightly concave lip, and the latter has a 
pair of glands at the base which secrete nectar, which is stored up in the 
cavity just in front of them. The arrangement is such that an insect 
crawling into the flower to get at the supply of nectar can hardly avoid 
touching the points of the rostellum, and on withdrawing would bring away 
the viscid gland with the attached pollinia, to be in turn left on the stigma 
of the next flower visited. 
The union of the pollinia with the glands of the rostellum is interesting, 
and shows how completely all the parts are adapted for the functions they 
have to perform. Long before the flower opens, each lobe of the anther 
splits gradually from base to apex, allowing the included pollinia almost to 
touch the upper part of the rostellate points. The pollinia then emit a 
number of excessively delicate thread-like projections, which reach the 
rostellum, and become firmly attached to it. So that, ina fully expanded 
flower, each set of pollen-masses is quite free from its anther cells, but they 
are firmly attached by their bases to their respective rostella, neither of 
which can be removed without bringing away the pollinia. R.A.R 
