African and Madagascar Flowering Plants. 363 
anthers is also in contact by their basal lobes ; a slit is, how- 
ever, left between the tip and their basal ends as their sides 
are not quite straight ; pollen is produced chiefly by the upper 
part of the anther (above its insertio ), but a slight amount is 
also found in the basal lobes. The style ends in a thickened 
extremity of which the uppermost part seemed to be barren ; 
below the level of the polliniferous portion of the anthers, 
however, it bears a membranous ring, which is formed of ten 
coherent scales with free triangular tips ; these triangular tips 
are alternately opposite the thickened insertion of the fila- 
ments and the entrances to the above-mentioned spiral hollows ; 
those which are opposite the hollows are horizontal, and occupy 
most of the entrance whilst the others are reflex on the style. 
The true stigma appears to be underneath this ring, and is 
therefore protected by it from most of the flower’s own pollen. 
It secretes a sticky matter. We are now in a position to 
understand the mechanism of the flower. If a bristle is intro- 
duced into one of the circular openings, its tip follows the line 
of the corresponding spiral groove until it reaches the base of 
the flower and nectary ; during the insertion, moreover, it is in 
contact with the corolla-tube through its whole length. Im- 
mediately, however, one withdraws the bristle, it straightens 
and slips between the horny basal lobes of two anthers so that 
on withdrawal, being rendered sticky by the secretion of the 
style above mentioned, it removes the pollen heaped up on 
the top of the style. The triangular tip of the stylar mem- 
branous ring will scrape off any pollen which may be on the 
proboscis on entering the corolla-tube of another flower. 
Cross-fertilisation would be therefore effected by, for instance, 
the proboscis of a moth. Self-fertilisation, however, is not 
wholly excluded, as the pollen of the basal lobes of the anthers 
might easily come in contact with the stigma. Visitors : — 
Probably night-flying moths. Beetles (No. 467) are often on 
the flowers gnawing the corolla. 
Vinca rosea, L. (Figs. 95-97). 
The flowers are red and have a long corolla-tube, which 
is enlarged at the insertion of the stamens, but only half a line 
