SCIENTIFIC SUMMARY. 
89 
BOTANY. 
Sensitive Organs in the flowers of Asclepiacls. — Dr. J. Gibbons Hunt com- 
municated to the Academy of Natural Sciences of Philadelphia, on the 
27th of August last, some observations on the flower of Asclepias asterias , 
which he had been informed by Mr. Isaac Buck was probably a fly-catcher. 
The odour of this flower, which is exceedingly disagreeable to human olfac- 
tory organs, appears to be very attractive to flies, many of which were 
watched by Dr. Hunt 11 eagerly applying their tongues all over the petals 
and essential organs, apparently eating with almost intoxicated relish the 
attractive excretion covering those parts.” They continued to indulge freely 
in this banquet until they happened to touch one of five black spots placed 
alternately with the stamens, when the fly was immediately seized and held 
fast by his proboscis. In the struggle that ensued the fly, if small and weak, 
would be held fast in the trap ; if large and strong he would make his escape, 
but burdened with the trap and with a pair of pollen-masses attached to the 
latter. The adhesion of the fly’s proboscis to the black spots is not due to 
any sticky fluid ; but it is caught by an organic structure, the action precisely 
resembling that of an ordinary rat-trap. The sensitive black discs may be 
set in action by contact with a bristle. 
Analogous arrangements occur in other genera of the Asclepiadece , and on 
the same occasion Mr. Edward Potts gave an account of his observations on 
two species of Asclepias (A. incarnata and curassavica ) in which similar 
phenomena take place. The sensitive organs are placed immediately below 
the anther-sacs in shallow depressions upon the perpendicular ridges of the 
stigma. Two pollen-masses are attached to each clasping organ by long- 
bent filaments, and these are withdrawn from the anthers when the organ has 
clasped the leg of an insect, a bristle, or a small camel-hair pencil. As evi- 
dence in support of this arrangement being destined to cause cross-fertiliza- 
tion, Mr. Potts mentioned his having found upon flowers of Asclepias curas- 
savica foreign sensitive organs with their attached pollen-masses, which must 
have been brought there by some external agency. In each case one mass of 
the introduced pair was inserted under the edge of the anther of the flower, so 
as to come close against the sloping lower surface of the stigma ; the flowers 
thus intruded upon persisted longer than others of the same group, and on 
dissection it was found that each of the inserted pollen-masses had sent out 
a profusion of pollen-tubes towards the junction of the stigma and the 
style. 
A Catalogue of British Plants. — We understand that the Rev. George 
Henslow, E.L.S., is about to print a catalogue of British plants arranged 
according to “ Hooker’s Students’ Flora.” Anyone wishing for copies is re- 
quested to communicate with him, at No. 6 Titchfield Terrace, Regent’s 
Park, N.W. 
The “ Pro-embryo ” of Char a. — In the 11 Journal of Botany” for July last 
Mr. A. W. Bennett, writing on the systematic position of the Characece , 
proposes to unite that order with the Muscinece ; later Prof. Oaruel assigned 
it a position between the vascular cryptogams and the phanerogams ; and 
in a still later paper Mr. Sydney Vines looks upon it as an independent 
group, intermediate between the Carposporece and the Muscinece. Both Mr. 
