THE NATURAL HISTORY OF THE FLOWER. 291 
When the flowers were placed in the open air on a warm day 
in August, they were visited by various Syrphidew and by species 
of Bombus and Apis. From the general size of the parts and the 
absence of free honey, it would seem probable that the flower is 
adapted for large bees. 
Another point that still requires explanation is that the viscid 
matter of the rostellum does not set at once, as is usually the 
case in orchids on exposure to air*, but takes from 12 to 24 
hours to do so; hence, unless the pollinia are very firmly pressed 
on to start with, they are easily knocked off subsequently. 
The smoothness of the labellum appears to be due to a very 
thick cuticle on its epidermal cells. This can be stripped off 
without difficulty in pieces an inch square. 
The bucket portion of the labellum is lined with stout hairs ; 
the cells of these and of the outer layers of the subjacent tissue 
have deep red-coloured cell-contents. They appear also to 
contain sugar (?). 
Pimelea decussata, R. Br., var. diosmefolia, Meisn. (in DeCan- 
dolle, Prod. xiv. p. 503).—The flower was studied upon a fine 
plant in the Cambridge Botanic Garden; when in bloom it is 
very conspicuous, every twig ending in a head of about forty 
pink-coloured flowers somewhat loosely arranged. The reddish- 
coloured perianth is tubular, 12 mm. long and 1 mm. wide at the 
mouth, with a spreading limb of four segments whose total width 
is about 7mm. The anterior and posterior segments are usually 
bent slightly downwards (Pl. XIX. fig. 11). The tube is hairy 
outside ; on the lower part the hairs are long and horizontal, on the 
upper part shorter and directed upwards. The two stamens are 
inserted on the throat, opposite to the anterior and posterior 
segments of the perianth ; they project beyond the perianth, and 
the pollen is thus exposed freely, as in so many dry-climate plants. 
The ovary consists of one carpel with a lateral style and capitate 
stigma. 
The flower has no scent; honey is secreted by four glands, 
two on the anterior, two on the posterior side of the base of the 
ovary. It is well protected from rain or short-tongued insects 
by the long perianth-tube. 
When the flower opens we see the two stamens sticking out, 
somewhat diverging from one another, with open orange-coloured 
* It is of course always, to some extent, exposed to the air before the pollinia 
are removed at all. 
