242 
strictly confined to their supposed home, and that their occur- 
rence in edaphically favorable places in the Kittatinny mountains 
was an example of such phytogeographical instability. A careful 
reading of Dr. Britton's paper shows that not only did he make 
no such claim, but that all the plants mentioned there, with one 
exception, are not pine-barren plants, strictly speaking, at all. 
They are all merely plants of the sandy coastal plain, Corema 
Conradài, a true pine-barren plant, being the one exception. The 
distribution of this species and of the many others now found 
isolated outside of the pine-barrens, is to be sought in the post- 
glacial history of the region to the north. In the general vege- 
tative scramble, so to speak, to cover the country uncovered 
by the retreating ice, it seems natural that those plants whose 
ancestral home had been in sand, should * choose" sand as a 
stopping place. It would, in reality, be strange if they had done 
anything else, and it is significant that all the plants mentioned 
by Britton are sand plants. 
АП of these evidences,—the geological history of the country, 
the isolation of Beacon Hill and the consequent isolation of the 
ancient pine-barren flora upon it, the post-glacial migration of 
some of the pine-barren species, and finally the present distri- 
bution of the pine-barrens, coinciding as it does so closely with 
the Beacon Hill formation, seem incontestably to point to a 
geological explanation of the origin and present distribution of the 
pine-barrens. Such a conception of the origin of this phyto- 
geographical region entails a readjustment of our ideas as to the 
relative age of the flora and of some related phenomena; for, if 
this theory is correct, then the pine-barrens can no more be con- 
sidered as a new or pioneer vegetation, but rather as an old and 
climax condition, ancestrally infinitely more ancient than any- 
thing in the surrounding area. 
BROOKLYN BOTANIC GARDEN 
docui ale Š : S г 3 Sh esc К a 
5 p p Am am cM ee СӨ ОЕР M 
телеси Оет КГ 
