726 Mr. Brown on the Organs and Mode of 
the obstacles opposed to them; and such tubes very seldom 
enter the style, but along with others hang down externally be- 
low the joint. This introduction of part of the tubes into the 
apex of the style is soon followed by a manifest enlargement of 
the ovarium, and of the style itself, which, in Asclepias purpu- 
rascens, then exhibits a discoloured blackish line, visible even 
on the surface of its inner side. On opening the cavity or body. 
of the style in this stage, a fasciculus of tubes was constantly 
seen passing down the centre, which was originally pulpy, and 
the walls of the cavity formed by the passage of these tubes 
was always found indurated and blackened, having every ap- 
pearance of being absolutely killed. 
I have never been able hitherto to follow these tubes further 
than the commencement of the placenta, where they really ap- 
pear to terminate*. I have not at least yet succeeded in tracing 
any of them either on the surface or in the substance of the pla- 
centa, though with this object I have examined it not only in 
its first degree of enlargement, but also in some of its more ad- 
vanced stages. 
The same series of appearances, with very slight modifications 
only, were observed in all the species of Asclepias (not indeed 
more than seven in number) which I had opportunities of ex- 
amining during the summer. For in those species in which the 
pollen mass was not found transferred from its original position 
to the fissure, and in contact with the base of the style, no doubt 
by means of insects, it was not difficult to place it there; and in 
doing so I never failed to obtain the same results. 
I now turned my attention to the base of the stigma, expecting 
to find there such a modification of surface as might serve to 
account for the rupture and production of the tubes in the mass 
brought in contact with it. I have, however, in no case been 
* 'Tab. 34. fig. 10, & 11; and Tab. 35. fig. 5, & 6. 
able 
