МЕ. Т. Н. CORRY ON ASCLEPIAS CORNUTI. 179 
them, seems also to have arrived at the true fundamental idea as to the method of their 
formation, viz. by secretion or excretion from the cells lining the furrows, though he 
unfortunately employs the term “ glands of the stigma " to designate them when fully 
formed, and so his description of them, fairly good in many respeets,* is misleading. 
Payer believed that the corpusculum was really a secretory gland, whose secretion gave rise 
to the corpuscular appendages, an idea which is thoroughly erroneous. No one appears 
to have ascertained, previous to the present investigation, how the superior boundary 
of the corpusculum was formed, or most of the other details of the foregoing account. 
While the corpusculum is being developed in the manner above detailed, certain 
other changes have also been taking place. At the period when the corpusculum has 
the form of two separate elongated masses of partially hardened gum, the epidermal 
cells of the style-table become papilliform along the region of two lines, which diverge 
laterally from the sides of the wider and deeper excreting portion of each furrow a little 
below its middle at an acute angle and have a downward oblique direction (fig. 16). 
The effect of this is to cause the excreting part of the furrow to broaden somewhat at 
the point of divergence of the lines, and from ovate-oblong to become more or less 
rhomboidal in shape. This change in shape on the part of the furrow naturally 
determines the external form of the corpusculum to a certain extent, for when mature it 
has a form between ovate-oblong and rhomboid. The epidermal cells, which become 
papilliform in the region of the two lines, do not all extend to a uniform length, but 
some are longer than the rest, so that along each line a shallow groove, і. е. a more 
superficial depression than the main furrow, is produced, which later is lined by papilliform 
cells and bounded by a series of cells forming longer papillee, these last in turn gradually 
fading off laterally on either side into the ordinary epidermis of the style-table. The 
cells of these diverging grooves (which grooves are in some cases extremely short, but in 
the species 4. Cornuti of considerable length, so as to be at least three times the length 
of that part of the main furrow which excretes the corpusculum) exude, like the main 
groove, a viscid matter. This occupies the intervals between the projecting rounded free 
ends of the papille, just as in the case of the formation of the corpusculum ; and the 
excretion appears, іп this case, to begin simultaneously from ай the cells which line the 
narrow furrow. The degree of hardening which the gum attains is never so great as in 
that of the corpusculum, owing in part to the comparatively late period of development of 
these diverging furrows as compared with that of the main furrow, and also partly to their 
being, even when the flower expands, carefully protected from exposure to the air by the 
anthers and anther-alee, which closely overlie them. Тһе amount of successive exudation, 
from the cells lining each of the narrow furrows, then, is only sufficient to cause the 
formation of а single compact solid mass of partially hardened gum, which for some time 
previous is in a semifluid condition, but when completed is wedge-shaped when cut trans- 
versely, and has a slight yellow colour or is brownish in its thickest part. Into the inferior 
surface of this mass the ends of the excreting cells still project, and on the broad margins 
of the furrow outside the edges, where the epidermal cells are still somewhat papilliform, 
ж Memoirs of the Wernerian Natural History Society, vol. i. 1808-1810, рр. 12-15, Edinburgh, and Misc. Bot. 
Works, vol. ii. pp. 195-199. 
