239 
been mere chance at first, then increased perhaps by the greater 
ease of one species as against its neighbors in getting its food, or 
to the failure to get food without some such reciprocal relation. 
The inference that this non-autophytic habit is due to isolation 
and consequent necessity of seeking other than "regular" 
methods of getting food, in a region, perhaps ancestrally offering 
an inaccessible food supply, may not be without significance. 
It is certainly of interest in this connection to note the well 
known high percentage of monocotyledons,” Pinaceae, Fagaceae, 
Scrophulariaceae, and Ericales, all of which are mostly non- 
autophytic." бо far as Orchidaceae and some of the mono- 
cotyledonous families are concerned the number of species is 
disproportionately large as compared with the surrounding 
country. Among some families, Fagaceae, Pinaceae and Eri- 
caceae for instance, it is the number of individuals that is so 
great, forming practically exclusive growths in the case of Pinus 
rigida and Chamaecyparis thuyoides. 'This very general preva- 
lence of the non-autophytic habit may have had something to do 
with the failure of many wholly autophytic plants, surrounding 
the Beacon Hill formation, to gain a foothold there, for the 
mutual exclusiveness of the diverse habits is obvious. There 
may, however, have been quite other factors operative here than 
antiquity and isolation. It would be interesting in this con- 
nection to compare the flora of the pine-barrens with some other 
region of similar geological antiquity. The driftless area of 
Wisconsin seems, at first thought, to be similarly conditioned 
geologically, but there is evidence that it could not have been 
steadily vegetated during the Pleistocene, as it was covered by 
water during some part of this period.” 
The extra-territorial distribution of some of the typical pine- 
% Stone, W. loc. cit. X See also Harper, R. M. Torreya 12: 224. 1912. 
Torreya 5: 207-210. I9 
27 According to E pe (Der Sinn der мск in Jahrb. Wiss. Bot. 
34: 539-668. 1900) in the following families many, not all the species, are 
mychorhizal, Orchidaceae, —€—— ied кора end p Saxi- 
— Fagaceae, чырк каи: Gentianaceae, Ericaceae, Scrophulariaceae and 
Conife There are many other individual case 
28 ege оаа di C., and Salisbury, R. ig Driftless area of the Upper 
Mississippi Valley. Ann. Rept. U. S. Geol. Sur. 6: 199-322. 1885. 
