OF THE ROSTELLUM OF LISTERA OVATA. 
261 
posed of a grumous fluid full of minute transparent chlorophyll-globules of various 
dimensions. As they advance to maturity, the cell-walls disappear, and the whole 
tissue appears more uniformly grumous ; on its first discharge from the rostellum, 
it presents the appearance of a glairy fluid, charged with transparent granules, acieular 
raphides, and traces of an hexagonal cellular tissue or rete. 
The expulsion of the contents of the loculi is no doubt the natural effect of the 
distension of the latter, which causes the rupture of the apex of the rostellum at 
two points. Whether the simultaneous discharge of all the loculi is wholly a 
mechanical, or in part a vital action, may possibly be doubtful ; if the latter, it may 
present some analogy to the simultaneous protrusion of the tubes from all the pollen- 
grains forming the pollen-mass of Asclepias Curassavica, first indicated by Mr. Brown. 
In one instance, however, I succeeded in causing the contents of each loculus to be 
voided separately in vermiform masses, by compressing an immature fresh rostellum 
in water. 
Soon after its emission the viscous mass hardens, becomes reddened, and usually 
adheres very firmly to the apex of the rostellum. Jt is not acted upon by iodine 
beyond being faintly browned. 
The membrane of which the walls of the loculi are composed is excessively thin 
and transparent, and presents a beautiful appearance under the microscope ; each line 
marking the position of the septa being' bordered with a band, which is composed 
of excessively fine, straight, oblique or wavy striae, which are placed at right angles 
to the septa. 
The position and function of this glandular secretion naturally recall the theory 
once proposed to explain the impregnation of Orchidece, which assumes that ope- 
ration to take place in many species of the Order through the glands at the base 
of the pollen-masses ; I therefore sought diligently for any facts that might coun- 
tenance such a supposition in Listera , but in vain. I was unable to detect pollen- 
tubes in the glandular body at any period; and I repeatedly spread the pollen 
over the viscous matter when under the microscope, but without any effect ; on the 
other hand, those pollen-grains that were ^placed on the stigma emitted boyaux 
abundantly. 
In a morphological point of view, the exact nature of this complicated and highly 
organized rostellum is not very evident; but it may be remarked, that its position 
would suggest a theoretical relation with the two undeveloped stigmata of the natural 
order, whose position may be supposed to coincide with that of each half of the 
rostellum. The blending of the different suppressed organs forming the column of 
Listera is, however, so complete, that in the present state of our knowledge it is 
perhaps safer to regard this curious organization of the rostellum as an accessory 
stigmatic organ, or appendage to the stigma, such as those which occur in various 
natural families of plants, and more or less directly facilitate the office of im- 
pregnation. 
