Oct. lo, 1872] 



NATURE 



479 



are joined to,5Cther from the base to the apex. The stamens 

 are diadelphous, the filament of the tenth stamen being 

 separate at the summit and base, and separable in the 

 middle (see Fig. 3). They arc of nearly equal length, 

 the pollen is abundant and rather moist, and is shed at 

 the lime the blossom expands. The upper parts of the 

 filaments arc stilT enough to keep their place, but not so 

 stiff as the style. The lower parts of the filaments form 

 a stiff tube, expanded towards the base, sD as to leave a 

 large cavity round the base of the ovary. This cavity is 

 abundantly supplied with nectar. On each side of the 

 tenth stamen at its base, there is a wide aperture, through 

 which apertures, on removing the ve.xillum, thii civity 

 villi its nectar is easily seen (see Fig 4). 



sation were the rule, the elaborate structure I have de- 

 scribed is meaningless, whilst if the purpose is that 

 insects shall carry the pollen from flower to flower,- it 

 becomes a curiously elaborate and complete piece of 

 mechanism having a special object. The change of 

 position of the flower by the bending, straightening, 

 and second bending of the pedicel, so that the ten- 

 der opening bud and the young fertiUsed ovary are 

 protected from rain and cold ; whilst the open blos- 



Fic. 4.—Pis:im sathiim (ront viewof stim'n.il tiilio, willi lenth st.im=n, 

 front showing apertures into nectary on each side the lube). 



The style is at right angles to the horizontal ovary, and 

 curves towards the vexillum at the top. The stigma is at 

 the extremity, and faces outwards and upwards towards 

 the vexillum. On the inside for some distance below the 

 stigma it is clothed with stiff hairs, which are set so as 

 to point upwards towards the stigma (see Fig. 5). The 

 style appears to be formed by two folds of the carpellary 

 leaf, which bend outwards from the point where the style 

 joins the ovary, so that the outer side or back of the 

 style which lies towards the suture of the keel, and which 

 has no hairs on it, is formed, not of the outer suture o f 

 the carpel, but of the edges of these folds. 



At the time the flower opens the stamens have shed, 

 or are shedding, their pollen, which lies in an abundant 

 mass at the apex of the keel around and above the stigma. 



5.-/'"«.v/ i 



/ (pislil). 



The back of the stiff elastic style almost touches the 

 keel ; and on pressing down the wings, which, as above 

 noticed, are attached to the keel, the back of the style, 

 which has no hairs, is pressed against the keel, whilst the 

 brush on the front and sides of the style sweeps the moist 

 pollen upwards and pushes it out of the apex of the keel 

 and against any object which is entering the flower, and 

 to which the pollen, being moist, will adhere. On re- 

 moving the pressure the parts take their place again, 

 whilst on repeating the pressure the same process may 

 be repeated, until the whole of the pollen in the upper 

 part of the keel is brushed out. 



As soon as the flower closes and before it withers, the 

 pedicel again droops, the flower becomes pendent, and 

 the calyx again acts as a pent-house to the young pod 

 (see Fig. i). 



Now, undoubtedly, the stigma of one of these flowers 

 is always covered with its own pollen ; but if self-fcrtili- 



Fi.:, 6 -/.„//;jv/M(k.:el an J pi-ti^. 



som displays itscli' in the most atti-acti/e and con- 

 venient form and position for insects ; the con- 

 spicuous vexillum ; the wings, forming an alighting place ; 

 the attachment of the wings to the keel, by which any 

 body pressing on the former must press down the latter ; 

 the staminal tube inclosing '[iiectar, and affording by 

 me.tns of its partially free stamen with apertures on each 

 side of its base, an open passage to an insect seeking the 

 nectar; the moist and sticky pollen placed just where 

 it will be swept out of the apex of the keel against the 

 entering insect ; the stiff elastic style so placed that on 

 a pressure being applied to the keel, it will be pushed up- 

 wards out of the keel ; the hairs on the style placed on 

 that side of the style only on which there is space for 

 the pollen, and in such a direction as to sweep it out ; 

 and the stigma so placed as to meet an entering insect, — 

 all these become correlated parts of one elaborate mechan- 



ism ; if we suppose that the fertilisation of these flowers 

 is effected by the carriage of pollen from one to the 

 other. 



I have, however, not observed the bees or other insects 

 at work on these flowers, whilst they are to be found in 

 abundance on the neighbouring broad beans and scarlet 



