MR. T. H. CORRY ON ASCLEPIAS CORNUTI. 189 
at all glutinous or adhesive, as Prof. Asa Gray regards it to Бе”. Оп the contrary, in 
the mature corpusculum its whole internal surface is firmer in texture, darker in colour, 
and older in point of development than the external surface; and as this anterior 
boundary forming the margins of the fissure is the earliest part of all to be developed, it 
possesses the above-mentioned features in a preeminent degree. 
From the time of Kólreuter t onwards various observers, Sprengel among others, and 
in recent years an American investigator, Mr. Edward Pott i, have either imagined or 
held that the corpusculum possesses the elasticity of a trap, so that when the leg of the 
insect comes between the two sides of the fissure and touches them, they immediately come 
together and, closing on the member, hold it fast. The last-named gentleman, who 
worked with the species Asclepias curassavica, L., and A. incarnata, L., describes the cor- 
pusculum as being both ‘ sensitive” (irritable) and * contractile," the former property 
residing in the posterior (inner) surface, the latter in the parts of the anterior surface 
which bound the fissure. He mentions that, on stimulation of the posterior surface of 
the corpusculum by contact with a foreign body, contraction of the part forming the 
margins of the fissures takes place, so that these margins are quickly approximated, and 
the fissure is almost closed. 1% is almost needless to say that the endowment of an inert 
body, such as the corpusculum is, and such as I have developmentally proved it to be, 
with properties which belong only to diving protoplasm is purely imaginary and fanciful, 
and is, moreover, founded on misinterpreted observations. | 
If the insect has drawn out a pair of pollinia, it sometimes makes efforts to remove 
them, but always in vain. The two pollinia, immediately after their extraction from the 
anther-cells, stand widely apart, with their less convexly curved edges, which, when Фи situ, 
are directed towards the sides of the cells next the alar fissure, facing one another. Their 
more convexly curved edges, which in situ are directed towards the median line of the 
anther, stand away from one another; for up till this time the gum composing the corpus- 
cular appendages has remained moist and semifluid, being still attached to the excreting 
cells of their furrows and not being exposed to the air, for they are hidden from view by 
the anthers which lie closely upon them. А few moments after the whole corpusculum 
with the pair of pollinia attached to it by means of its “ appendages” is withdrawn, the 
* appendages," being exposed to the air, dry up. During this process they undergo 
peculiar movements, being rotated inwards on themselves rather below their middle por- 
tion in such a manner that the two pollinia fold together towards that side which formerly, 
when the whole apparatus was 2% situ, faced the centre of the flower, and are drawn so as 
to lie close to one another, with their broad diameters nearly parallel. In this manner, 
and by means of these movements, they attain exactly that position in which they can 
with ease be inserted or pushed into the lower cordate expansion of one of the five alar 
fissures leading to the truly stigmatic portion. The insect, being now furnished with 
these pollinia, proceeds with its work of collecting honey, either from the nectaries 
ж с Structural Botany,’ 1880, p. 324. 
+ « Anthera contortum," * Actorum Academis electoralis Theodoro-Palatine У.” vol. iii. Physic. 1775, р. 41 
et seq. 
+ * Proceedings of the Academy of Natural Sciences, Philadelphia, 27th Aug. 1878, pp. 293-296, figs. 1-4, 
SECOND SERIES.— BOTANY, VOL. II. 2G 
