260 
DR. J. D. HOOKER ON THE FUNCTIONS AND STRUCTURE 
being uniform till it acquires its broad tongue-shaped form in the mature flower, when 
it is about ^ 0 -tb of an inch in length and breadth. In this state it is rather concave 
upon the upper surface, slightly raised along the mesial line, and with somewhat 
upturned edges and apex. The margins are tolerably thick, and the apex presents 
a broad central point, with a shallow sinus on either side of it. The substance is 
extremely soft, white, semi-transparent and pulpy. Both upper and under surfaces 
are marked with 30 to 40 delicate parallel strise, which along the mesial line are 
straight, while those on either side of it converge towards the apex of the rostellum, the 
marginal ones being conformable in direction with the outline of that organ. Towards 
the very apex, these parallel lines are crossed by a few transverse bars (indicating 
their cellular origin), and at the base they rest upon, or gradually pass into, a papillose 
cellular tissue, which is continuous with the surface of the column. Two darker 
areolae are observable at the termination of the rostellum, occupying the shallow sinus 
on each side the apex ; and these indicate the points from which the viscous masses 
are ejected through the rupture of the tissue of the cavities containing them. 
After the discharge of its viscous contents, the rostellum collapses considerably, 
its apex and margins become deflexed, and the pollen-granules are allowed to fall 
over on the stigma. 
A transverse section of the rostellum shows that it is wholly formed of continuous 
longitudinal parallel loculi, corresponding in number with the strise on the surface ; 
these are separated by septa of excessive tenuity and transparency, but of considerable 
firmness, and these, as well as the walls of the loculi, present no traces of areolation 
or cellular structure, except towards the apex and base of the rostellum. The loculi 
are many times longer than broad, and are much less in width than in depth, their 
diameter between the two surfaces of the rostellum being about 1^ times greater 
than that between the septa, whence the appearance presented by a transverse section 
of the whole organ is that of a galvanic trough of 30 to 40 cells. 
Owing to the exceedingly pulpy and transparent character of the rostellum, its 
irritability, and the viscous nature of its contents, I was wholly unable to understand 
its structure in the living plant, and had recourse to specimens preserved in spirits 
three years ago by Professor Henslow. 
On opening the loculi, each was found to contain a very elongated club-shaped 
body, conformable in shape to that of the loculus (whose form might hence be deduced 
from that of its contents). These bodies, which are the viscous secretion of the 
rostellum in a hardened state, were very much flattened laterally, gradually narrowed 
upwards into slender points, with somewhat swollen tips, slightly curved and obliquely 
truncated at the base. Their bases, or rather those of the loculi which contained 
them, rested upon the loose cellular tissue of the column, which was distended with 
fluid, chlorophyll and acicular raphides. 
In their youngest condition these club-shaped bodies are more opaque, and appeal- 
covered with hexagonal areolae (an indication of their cellular origin), and are com- 
