MR. T. Н. CORRY ON ASCLEPIAS CORNUTI. 203 
papillar tissue leading from the stigmatic angles into the interior of the styles, he was not 
aware that the rest of the inferior surface also was papillar, since he says **that he has 
never been able to decide whether the five cords enter the two styles unequally divided 
into two and three, or whether they unite just before their entrance into a circle which 
is then distributed in two equal portions in the two styles. It is just at the point where 
the apices of the two styles join and unite with the style-table that a separation between 
these two parts ultimately takes place; and Brown appears to have regarded such a sepa- 
ration as a necessary event previous to the introduction of the skein of tubes into the 
tissue lining the style, in order that the entrance to the apex of the style should be open 
and freely exposed. That it is not absolutely necessary is, I think, clear from the 
observations of Brongniart, which accord with those just detailed of my own, both of us 
having directly observed penetration of the skein from the stigmatic tissue into the tissue 
of the style without any separation of parts; and this is, moreover, evident а priori from 
the fact that the tissue of the two parts is continuous. But that such a partial separation 
on the inner side of the style is of advantage І will not deny, since by this means a suffi- 
cient aperture is afforded through which the whole of the tubes forming the skein may be 
readily inserted ; while in the simpler case, which has been first alluded to, owing to the 
skein being composed of a great mass of tubes, only a portion of them are able to find 
room to penetrate in the continuous tissue, while those which are unable to do so become 
bent, and their free ends hang down externally below the joint. Brown also found that 
a certain number of tubes were excluded, even though the separation did take place, if it 
happened to be insufficient to admit the whole girth of the skein. Iam, however, dis- 
posed to think that in many cases the separation of the two parts is due, partially at any 
rate, to the introduction of a portion of the skein of tubes from the stigmatic tissue into 
the tissue lining the centre of the style, which tubes then enlarge, causing lateral rupture 
of the apex of the style, and that then separation of the two parts follows. The tissue 
forming the centre of the style, in the middle of which the skein of pollen-tubes may be 
found making its way downwards, is soft and pulpy in texture, formed of transparent 
oblong cells with very thin walls, which appear white e» masse. These cells are inter- 
mediate in character between those which form the papillar tissue of the receptive surface 
and those which form the external or superficial portion (2. е. that nearest to the ventral 
suture) of the placenta in the ovary. At its upper end they partake more of the character 
of the former tissue, while at its lower end they come nearer to that of the latter. This 
tissue is easily distinguished from that which forms the external part of the style, and 
is continued upwards from that forming the exterior of the ovary, ?.е. the pericarp. 
The name * conducting tissue" has been aptly applied to indicate the similar function 
both of this tissue and the papillar tissue forming the true stigma. The course of the 
skein, which has now become exceedingly long, in the conducting tissue of the style is 
rendered obvious from the exterior by a dark line on the surface of the style near the 
suture, and from the interior by the walls of the passage, formed by the skein absorbing 
the tissue as it travels, being blackened and rendered dead, their texture being altered 
and somewhat hardened. The pollen-tubes themselves are rendered very evident by 
staining with iodine. The style itself increases considerably in girth, and the ovary 
