OF PERIODIC PHENOMENA. 333 



influence, necessarily affecting them all equally. 

 And it follows that those which occur together any 

 one year, will occur at or nearly the same time every 

 other. It would not be difficult to make out a long 

 list of such coincidences, the phenomena in which 

 they appear being either instances from the vegetable 

 kingdom alone, or from the vegetable and animal 

 kingdoms together. Thus it has been noticed that 

 the biting stonecrop (Sedum acre), the vine (Fitis m- 

 nifera), and wheat (Triticttmhybernuiri), are all usually 

 coincident in their time of flowering, which is about 

 midsummer. A similar coincidence of date takes 

 place most years in the flowering of the catmint 

 (Nepeta catarid) and the purple loosestrife (Lythrum 

 salicaria), about a fortnight after Midsummer. 



Earlier in the season, we find the box (Buxus sem- 

 pervirens), and the ground-ivy (Nepeta glechoma), 

 opening their flowers most punctually together on 

 the 3rd of April, or thereabouts.* The bugle 

 (Ajuga reptans), and the horse-chestnut (jEsculus 

 hippocastanum), generally flower together, in like 

 manner, about the 3rd of May. 



As examples of coincidences between the periodic 

 phenomena of plants and those of animals, we may 

 mention Mr. Selby's remark,-)- that the black-cap 

 and willow-warbler never arrive in the north of 



* I find these plants flowering together on the 3rd of April, on 

 an average of nine years in the case of the box, and of eleven in 

 that of the ground-ivy ; and it is remarkable that the same date 

 stands equally against both of them in the Naturalist's Calendar 

 by White. 



t Quoted by Mr. Yarrell in his History of British Birds. 



