CALOTROPIS PROCERA. 53 
other plants of the same natural family. In Sarcostemma 
I should say the mass is itself cellular, the grains being 
lodged in distinct cells. This appears to be the case from 
the structure of the margin and crest, which last is obviously 
cellular: it is curious that though the crest is white, its de- 
hiscing thickened margin is yellow. 
n the structure of the margin, I am disposed to place 
considerable confidence: in all bodies consisting of cells, 
enclosed in a membranous sac the edges may always be seen 
very distinctly ; on pressure no inflection is to be seen. 
ut when a body is cellularly subdivided, and cells contain- 
ing others, no margin will be found, or if it should from any 
great thickness of the cells be discernible, it will not be a 
straight margin, but will follow the undulation of the marginal 
cells, and inflections will be found. The cellular structure has 
besides been shewn to exist in Asclepias by Mr. Bauer, and it 
is also in accordance with the observations of Mr. Brown. 
From part of those observations it would seem as if in 
some, (Asclep. purpurea) the mass was nothing but one of 
perfect pollen grains, so even the inner series is separable, 
and each grain has an outer tegument. 
The point in which Calotropis differs from the received 
mode of formation of pollen, is the simple membranous 
sac of the mass; the late appearance of the parent cells ; 
the absence of any thing like ternary or quaternary division. 
The nuclei forming the grains themselves—It certainly con- 
sists of a sac containing a quantity of simple cells, having large 
and small granules within. The membrane, composing the 
sac, is not itself cellular. 1 
he gland is at this time fully developed ; its crura however 
have not reached the pollen sacs, it is naked at both ends; 
ovula, etc. remain. 
The stigmatic tissue may be traced down to the articula- 
tion, or to the spot where the style begins to pass outwards ; 
towards this it becomes more and more indistinct, and less 
recognisable from the proper tissue of the style. The disc 
has a cellular whitish appearance, quite different from the 
angles and interangles. The ovula have a very short stalk: 
