DISTRIBUTION OF BRITISH PLANTS. 353 



known perhaps under its old name of OrnitJiogalum luteum, 

 and the Sweet Mag (Acorus Calamus), which is an interest- 

 ing plant, as being the only representative of the family 

 (Acoraceae), which is a native of Europe. It grows some- 

 thing in the same way as the Arums, except that the spike 

 of flowers, or spadix, is not enveloped by a rolled-up leaf, or 

 spathe, but grows bare and unprotected out of an opening 

 in (what looks like) the stalk, but is properly speaking the 

 spathe metamorphosed so as to look like one. 



It would be a great omission if we were to quit the sub- 

 ject of the Geographical Distribution of British Plants, with- 

 out becoming acquainted with the characteristics which dis- 

 tinguish the different zones of altitude on the British moun- 

 tains, which we will do under the guidance of Mr. Hewett 

 Watson, who, in his 'Cybele Britannica/ has reduced the 

 result of his observations on many different mountains and 

 hills to something like a systematic arrangement. The 

 method adopted is this : The order in which plants were 

 observed to occur in succession in descending different 

 mountains, and on different sides of the same mountains, is 

 given in separate columns. 



These lists of plants are then compared together, and a 

 strong general correspondence is found to prevail amongst 



2 A 



