40 



mature eyes which our childish notice thought to be quite grand. 

 Besides this, memory adds compound interest for the time which 

 intervenes, especially when a new-found importance attaches to the 

 principal. Besides this, it is by no means a settled thing that the 

 farmer's boy's plant was Calluna vulgaris. Taking Loudon's estimate 

 of the annual growth of heath, " three or four inches a season," or 

 even reducing this to two, twenty years would suffice for a seedling 

 plant to grow forty inches, which would make a respectable bushel 

 basket of branches. So that we need not suppose, with Mi-. Eand, 

 that these plants might in Mr. Livingstone's boyhood have been a 

 century old. Neither is Tewksbury such an " out-of-the-way place." 

 Billerica was settled in 1653, and we must not presume that a thickly- 

 settled population is necessary to introduce a foreign plant. One 

 stray seed from the pocket or bundle of a European immigrant may 

 have done it. Many instances have occurred where European plants 

 have been brought over in this way. Foreign plants frequently 

 spring up around paper mills from seeds brought in the rags used 

 there. They do not spread extensively, because the circumstances 

 are not favorable to their acclimation. In the case of the Heath, 

 this is an important point. Because, if native, there is no reason 

 why it should not be broadcast ; if it be introduced, there may be 

 nice, unperceived causes why it should not be acclimated here every- 

 where. The European violet even, common as it is in gardens, has 

 never established itself as an^ acclimated plant. If our gardeners 

 should sow the Heath everywhere, it might grow where it was 

 sowed, as it has done at Tewksbury, and thoroughly established it- 

 self, in spite of harrowing and mowing. This would prove pretty 

 conclusively, that were it a native, it would not have died out, as 

 circumstances would favor its growth as much now as ever. Instances 

 are very rare of an indigenous plant being confined, in any country, 

 to one half an acre of ground. 



A whole century and a half elapsed after the settlement of Billerica 

 before the Heath was seen there. The botanico-historic period did 

 not commence for a century and a half after its settlement. How 

 many opportunities might have occurred during that time for the ac- 

 cidental sowing of a foreign heath, when we know that there was con- 

 stant immigration from Europe, and know, also, that " the seeds retain 

 their vitality for many years." 



It is a question of considerable importance, as regards botanical 

 geography, whether the plants of Europe are identical, to any extent, 

 with those of America ; and therefore all the evidence bearing on the 

 nativity of the Calluna should be examined, whether in Tewksbury 

 or elsewhere. This evidence does not seem to be very direct or con- 

 clusive. ,It does not certainly prove It to be an inhabitant, either in 



