REV. G. HEXSLOAV ON THE STRUCTURE OF MEDICAGO SATITA. 327 



^ 



Note on the Structure of Medicago sativa^ as apparently affording 

 facilities for the intercrossing of distinct flowers. By tlic Jiev. 



GrEORGE HexSlow, M.A., F.L.S. 



[Read November 16, 1865.] 



Its the flowers of this plant, the vexillum is inserted by a short 

 claw, and is so folded as to leave a depression inside along the 

 medial line. The alse have slender claws, tliere being on the in- 

 side face of the limb of each petal a tooth-like process projecting 

 forwards, and which is also produced backwards parallel to the 

 claw. These latter backward extensions of the processes converge 

 over the stamens, and pressing on the staminal tube confine it in 

 its position. The petals of the carina present each a depression, 

 which receives the process projecting forward on the inner face 

 of the corresponding alary petal. The carinal petals cohere, and 

 include the extremity of the staminal tube and pistil, together 

 with the anthers. 



The walls of the staminal tube are remarkably thick, its li.ssues 

 being distended with fluid. The tissues become gradually thin- 

 ner towards the edges of the fissui-e on the upper surface. The 

 cells are of about the same shape and dimensions on both surfaces, 

 being more or less oblong and united by oblique ends. The aver- 

 age length is -00344 to '0046 inch, and breadth -00115 inch. Nine 

 small bundles of spiral vessels pass into the extremities of the free 

 portions of the filaments. 



The tube is at first horizontal, the extremity being concealed 

 Within the adpressed petals of the alse and carina ; but if any ob- 

 ject, as a pin, be directed down the channel formed by the vexil- 

 lum, its point will be conducted into the small elliptical space 

 between the alae, and immediately in front of the backward exten- 

 sions of the tooth-like processes. On pushing the pin further, it 

 can scarcely avoid pressing against these processes in a lateral 

 direction; the consequence is, that the tube is instantly released, 

 and springing upwards strikes violently the jexillum, and dashes 

 the pollen both against it and upon the pin, and then assumes a 

 vertical position and a rigidly curved form. 



The tenth or free stamen appears to have no independent elas- 

 ticity, but is simply forced upwards and bent by the action of the 

 coherent filaments. Having once become curved, it is impossible 

 to straighten the tube so as to make it assume its original position, 

 Without causing a transverse fracture. 



I have not been able to discover whether the cur\'ature is caused 



T^lNX. PROC. — BOTAWr, VOfi. IX. Z 



