March 3, 1916] 



SCIENCE 



325 



appear to have mueli to do with the age of our 

 local endemics, for it has been shown that some of 

 our most widely spread species are among the new- 

 est in point of origin. "Eeliot endemism" ac- 

 counts for 5 of the local species which are shown to 

 be outpost survivals of a preexisting flora. All of 

 these are species of endemic genera; only one is 

 woody, although these are probably the most an- 

 cient of all our endemics. Generic and specific 

 instability seems to account for the great major- 

 ity of our endemics, 14 in all. These species are 

 all shown to belong to genera that dwindle, or to 

 be related to species that are on or near their lim- 

 its, in the local region. Further support of this 

 view is given by the proportion of species in 

 eastern North American genera containing endem- 

 ics, to the number of species found in the rest of 

 the country and abroad. Only 20 per cent, of our 

 whole vegetation finds its limits in the area, but 

 much over half of our total endemics belong to 

 genera that dwindle, or are related to species that 

 find their limits, here or very near here. ' ' Habitat 

 endemism," where a species seems to have been 

 thrust off from a well-known and widely dispersed 

 form, into a totally different habitat from that of 

 the supposed progenitor, seems to account for two 

 of our local endemics. 



On the Occurrence of Pinus Sanlcsinna Lamb, in 

 the Driftless Area of Southeastern Minnesota: 



C. O. EOSENDAHL AND F. K. BUTTEES. 



The main pine forests of Minnesota occur to 

 the north of a line drawn from the northwestern 

 corner of the state to the Wisconsin boundary, 

 about latitude 45° 30'. Pimi^ StroMts L. is found 

 in a number of isolated localities down through 

 the Mississippi Eiver valley to northern Iowa, but 

 outposts of Pinus BanTcsiana are very unusual. In 

 June, 1915, a grove of jack pine was found near 

 Eushford in the Eoot Eiver valley, near the 

 southeastern corner of the state. This is aboat 

 one hundred and eighty miles south of the 

 previously known limit in this state and at least 

 eighty miles from the pine areas of central Wis- 

 consin. It lies inside the driftless area and the 

 indications are that it is a natural relict, prob- 

 ably from glacial times. The largest trees are 

 estimated to be from fifty to sixty-five years old, 

 thus dating back a few years beyond the oldest 

 settlement of the region. Associated with the 

 pines are a number of species which occur typically 

 in the jack pine forests. Among those noted the 

 following appear to be of special signficance: 

 Oryzopsis pungens (Torr.) Hitchc, Carex siccata 



Dewey, and Vaocinium pennsylvanicum Lam. The 

 grove is located on a very sandy, steep, north-fac- 

 ing hillside which is built up from disintegrating 

 paleozoic sandstones. 



The Distriiution of Quercus alba L. in the State 

 of Minnesota: F. K. Buttees and C. 0. Eosen- 



DAHL. 



The white oak, Quercus alba L., occurs in south- 

 eastern Minnesota, extending to a point about 

 thirty-five mUes northwest of Minneapolis and 

 somewhat farther due north of that city. It is 

 local in its distribution, but where it occurs it is 

 often very abundant. The explanation is that, at 

 least in the climate of Minnesota, it is exacting 

 as to its soil requirements and flourishes only on 

 well-drained, non-calcareous soils which are mod- 

 erately retentive of moisture. Such soils are the 

 residual clays of the unglaciated region, the less 

 calcareous portions of the loess, and the sour red 

 clays frequently found in that part of the Wis- 

 consin glacial drift which came from the north- 

 east, and on all these soils the white oak abounds. 

 The gray glacial clays from the northwest which 

 underlie the main deciduous forest region of cen- 

 tral Minnesota are generally too calcareous for 

 this species, and it has succeeded in penetrating 

 that region for only a few miles and in a few fav- 

 orable localities. Near the middle of the state are 

 some tracts of red clay similar to those which oc- 

 cur farther south and east, but no white oak has 

 reached them, its place being taken by a form of 

 Quercus macrocarpa Michx. It is suggested that 

 the region of calcareous clays has acted as a sieve 

 or selective barrier, allowing one of these species 

 to migrate freely while greatly retarding the prog- 

 ress of the other. Culture experiments support 

 the evidence derived from the distribution of the 

 species. In four years, a seedling white oak grown 

 in fine clean quartz sand grew about four times aa 

 large as a seedling of the same species planted in 

 sand containing five per cent, of chalk, while bur 

 oak seedlings grew almost equally well in the two 

 soils. 

 The Patanas of Ceylon: H. A. Gleason. 



The patanas, or natural grasslands of Ceylon, 

 occupy extensive areas in the southern end of the 

 island, mostly at high elevations. They are usually 

 located in valleys among the mountains, and at 

 their upper margin come in contact with the sub- 

 alpine forests. They occupy various types of soil, 

 and receive various amounts of rainfall, depending 

 on their location in reference to the mountain 



