iv.] ROSACES. 97 



1. Those in which the pressure of the bee pumps 

 out, as it were, a certain quantity of pollen ; the 

 flower resuming its original form when the pressure 

 is removed. (Lotus, Anthyllis, Ononis, and Lupinus.) 



2. Those in which not only the pollen, but also some 

 of the stamens are pressed out ; the flower resuming 

 its form on the removal of the pressure, as in the first 

 division. (Melilotus, Trifolium, Onobrychis.) 



3. Those in which the flower bursts on pressure and 

 ejects the pollen. (Medicago, Genista, Sarothamnus.) 



4. Those in which, on the pressure of the bee, the 

 pollen is swept out by a brush of hairs situated on 

 the pistil. (Lathyrus, Vicia, Pisum, Phaseolus.) 



The power of self-fertilisation seems to be lost in 

 some species of Phaseolus, Onobrychis, and Saro- 

 thamnus ; and to be much diminished in others, as in 

 Trifolium rep ens and Vicia fab a. 



ROSACES. 



This order contains seventeen British genera, includ- 

 ing Prunus (the Cherry, &c.), Spiraea, Geum, Rubus 

 (Blackberry, &c.), Fragaria (Strawberry), Potentilla, 

 Alchemilla-, Sanguisorba, Poterium, Agrimonia, Rosa, 

 Pyrus, Cratsegus, &c. 



Prunus. Our three species of this genus differ 

 somewhat in the relations of the anthers to the 

 stigma. In P. cerasus (the Cherry) both mature at 

 the same time, while in P. spinosa (the Black-thorn) 

 and P. padus (the Bird Cherry) the stigma reaches 

 maturity before the anthers : though as it retains the 

 capability of fertilisation after the anthers have opened, 

 the flowers are doubtless often self-fertilised ; which 



H 



