88 PEA, SCARLET RUNNER. [chap. 



together by four processes, two of which point forwards 

 and two backwards. These fit so beautifully that 

 the proboscis of a humble bee is sufficient to unlock 

 them, and release the stamens ; though, according to 

 Henslow, {Linn. Jour. 1866, p. 328) the hive bee is 

 unable to do so. Hildebrand, however, has observed 

 that in the absence of insects, it fertilises itself In 

 M. lupulina the elasticity is much less than in M. 

 sativa. Medicago is a honey-bearing genus. 



In the Leguminosse hitherto mentioned, when the 

 keel is forced open, both stamens and pistil emerge 

 from it. In Lathyrus (the Pea), however, this is not 

 the case. In L. pratensis, for instance, the stamens 

 do not leave the keel, but the pistil is provided with 

 a brush of hairs, which sweep the pollen before them. 



In the Scarlet Runner {Phaseolus communis) which 

 has been described by Farrer {Ann. and Mag. of Nat. 

 His. 1868, p. 25s), the keel is spiral, as well as the 

 stamens and pistil. The former are weak, and never 

 protrude ; while the pistil, on the contrary, is stout, 

 strong, and very elastic. In the natural position, the 

 stigma just protrudes out of the mouth of the keel, 

 while the terminal portion of the style within the 

 tube is covered with fine hairs. When, therefore, the 

 bee alights on a flower, and inserts her proboscis into 

 it, the stigma will come in contact with the base of 

 the proboscis, and will sweep off any pollen which 

 may be adhering to it. As, however, the bee presses 

 more on the flower, in its efforts to get the honey, 

 the pistil comes further out of the flower ; the stigma 

 turns upwards, away from the insect, and the brush 

 of hairs, which has swept the sticky honey out of the 



