CERTAIN SPECIES OF ASCLEPIADES. 51 
and pushing their proboscides eagerly into the flower. While 
thus scrambling over an umbel of flowers many of the pollen- 
masses are extracted, by the claws of their tarsi catching in the 
notched stigmatic glands. 
In the prime of their flowering most of the plants have their 
masses withdrawn before withering, and sometimes as many as 
two pollen-masses inserted in one fissure, although it is seldom 
that pollen-masses are inserted between all the al of one flower. 
The stigmatic glands* and arms to which each pair of pollinia 
are attached are edged by a delicate pale yellowish transparent 
membrane, which I am inclined to think is viscidulous. 
The stigmatic gland is deeply furrowed in the centre, narrow 
at the apex, and widely open towards the base. The arms, which 
are rather short, are bent upwards at their junction with the 
gland, then again downwards in a rather deep curve, and again 
upwards. The edging membrane is carried beyond to the point 
where the pollen-mass is attached. The pollen-masses themselves 
are somewhat truncated and quadrate. 
In the following descriptions the margins of each pollen-mass 
will be named in reference to their position in the anther-cells ; 
viz. that which faces the inner extremity of the cell will be called 
the inner margin, and that facing the fissure of the ale the outer 
margin. 
From the above description it is evident that if an insect, while 
scrambling over the plant, inserted the claws of its tarsus or any 
other hooked portion of its body, such as its mandibles &c., be- 
neath the gland, or if the claw got inserted towards the base and 
was then drawn upwards in the contracting channel of the gland, 
it would become firmly attached and easily withdraw the pollen- 
masses. 
Although the pollen-masses are often withdrawn by the tarsi 
of insects belonging to the Coleoptera, Hymenoptera, Hemi- 
ptera, and Lepidoptera, I am much disposed to doubt whether 
in most instances this mode would ensure the replacement of 
the gland in the fissures formed by the ale of the anthers. 
* In the description of the stigmatic gland and arms the latter are described 
relatively to the gland, and not to their position in theanther-case. Thus when 
they are spoken of as extending outward, it is in reference to the position of the 
gland, and not to the anther-case. I mention this in order to render the de- 
scription plainer, the margins of the pollen-masses themselves being spoken of 
in an inverse manner. 
+) 
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