348 Scott Eltiot .• — On the Fertilisation of South 
bulging of the carina, and, secondly, by the swollen basal 
auricles of the alae which project backwards covering similar 
though smaller lobes of the carina. 
An insect raising the vexillum causes explosion. (Cf. 
Sprengel, loc. cit. p. 363 on P. bituminosa.) Visitors : — Apis 
mellifica , very ab.—Cape Town, Oct. 
Psoralea pinnata, L . 
Visitors : — Hymenoptera : Large bee (? Xylocopa), Apis 
mellifica , etc. Lepidoptera : spp. — East London. 
Indigofera filiformis, Thunb . 
That the carina of this genus has an elastic tendency to 
spring downwards was pointed out so long ago as 1837 by 
Don, ‘ General History of Dichlamydeous Plants.’ The 
flowers of Indigofera macrostachya , Vent, have been excellently 
described by Delpino (No. 178, Muller); those of /. speciosa 
by Henslow (No. 323, Muller), and those of /. Dosua by 
Meehan (No. 385, Macleod). In this species I found exactly 
the same general structure. The carina has a very strong 
tendency to spring downwards (residing chiefly in the thick- 
ened claw), while the staminal sheath and claw have a distinct 
tendency to spring upwards. The inner edges of the carina 
are strongly thickened and fit over the staminal sheath, thus 
keeping the carina from descending ; the alae form a perfectly 
horizontal platform, being supported on conical projections of 
the sides of the carina (cf. ‘ Bollazione od ernie ’ of the carina 
of /. macrostachya , Delpino, 1 . c.) ; their inner edges, moreover, 
are grooved and fit over the thickened upper borders of the 
carina. This horizontal position seems to me to assist in 
keeping the flower from explosion in two wa ys, first, because the 
alae, if they are to allow the carinal edges to move outwards, 
must be twisted outwards in a plane which is the one in which 
they are expanded instead of being simply bent in a plane at 
right angles to their own surface, as would be the case if they 
were in the ordinary alar position, and, secondly , because the 
resultant of their weight (and that of a small insect stand- 
ing on them) is made to be directly downwards without any 
