or 



356 RET. a. HKXSLOW ox THE STEUCTUKE OE IKDIGOEEEA. 



ilhiirij to -which it will be guided by the projecting ridges on the 

 claws of the alse, and made to touch the point of insertion of the 

 carina, the latter immediately springs violently doAvn, and from 

 being in a horizontal position becomes vertical, by the claw be- 

 coming curved at right angles. The alse also fall laterally, having 

 lost their support. Tlie claw of the carina splits, and detaches 

 itself from the calyx, so that this as well as the other petals now 

 quickly falls off. 



In consequence of the sudden jerk thus caused by the fall of 

 the carina, a cloud of pollen is thrown upwards. The connectives 

 terminate in minute points, which by catching against the falling 

 carina may assist in dispersing the pollen, by 'forming a sort of 

 spring. 



In blossoms in which no insect or other means has effected tlie 

 fall of the carina, the claw of that petal will frequently be found 

 split, and the two extremities entirely detached from the calyx 

 and curling backwards, the carina, however, being sometimes re- 

 tained in its place by being entangled in the other petals. 



Since writing the above note, my attention has been called by 

 Mr. Darwin to a paper by Dr. Ilildebrand in the BotanischeZcitun 

 (March ISGG), in which he describes and figures the same con- 

 struction, assuming that it, as well as that of JMedieago sativa 

 (an account of which was read by the present writer before the 

 Society, Kov. 1SG5), is adapted for fertilization by insects. He 

 doc^ not, however, infer the probability that it is especially pur- 

 posed for the in/ercrossinff of distinct Jlowers — for othenvise it is 

 scarcely conceivable that it could be at all advantageous to a plant 

 to have its stamens and pistils so arranged as to be incnpable of 

 fertilization of itself, but yet only requiring its own pollen to be 

 transferred to its own stigma. Dr. Ilildebrand observed that 

 the discovery of this movement is not entirely new, as in DeCan-. 

 dolle's ' Physiology ' we find a description, though to a certain ex- 

 tent erroneous; for he says, " Certain corollas contribute, in a 

 direct manner, to fecundation: thus, e.g., the several parts of 

 the corolla in the species of ImVujofera and Medicago are bound 

 together by a kind of little 'spurj' when the corolla has 

 attained the end of its dcvelopnient, the 'spur' unfastens, the 

 nuconfined carina laps down and imparts a shock to the collected 

 stamens, the consequence of which is the falling out of the pollen," 

 Kow this I have already shown not to be perfectly accurate : 

 the " spurs " do not become unfastened, at least in McdicagQ 

 saiiva^ but the carina and ala? drop down in one piece ; and, more- 



