﻿1903] CURRENT LITERATURE 149 



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Dying xerophytes contain but little water ; while dying hydrophytes contain 

 much ; hydrophytes lose water more rapidly than the soil, xerophytes less so. 

 The per cent, of non-available water in a soil increases as the square root of 

 the per cent, of the soluble salts. 



W. A. Wheeler (Minn. Bot, Stud, 2: 353-416. 1900) has written an 

 ecological account of the vegetation of southeastern Minnesota. He notes a 

 wide difference between the vegetation of river and creek valleys. The 

 north-facing slopes, as so often is the case, have the climax vegetation of the 

 region. The moist cliffs contain some rare mountain plants, and some south- 

 ern trees find here their northern limit. The same author {idem 569-600. 

 1901) has presented a contribution dealing with flora of the Red river valley 

 in Minnesota, Some interesting halophytes and semi-halophytes are recorded. 

 Both articles are most beautifully illustrated with heliotypes, which are fully 

 described, — D. Lange {idon 621-630. 1901) gives an account of the 

 revegetation of Trestle island in Lake Phalen, Minn. This island was 

 exposed in 1898 and its successions of forms for three years are recorded. — 

 B. Fink {idem 657-709. 1902) continues his study of the lichens of Minnesota, 

 dealing here with those of the northwestern portion of the state. Lists of 

 characteristic species of sixteen rock, tree, and soil formations are given, 

 together with the characteristic adaptations. He discriminates between 

 granitic and limestone formations, and between exposed and shaded portions 

 in each ; between rough and smooth-barked trees; between live, dead, and 

 rotten wood; between upland and swamp trees (this seems especially inter- 

 esting, since Usnea dominates in each case, but with a much greater luxuri- 

 ance in tamarack swamps), etc. The author thinks that light and moisture 

 are much more important factors in lichen distribution than are either 

 chemical or physical characters of the substrate. It is to be hoped that 

 many more such papers will be published, as the reviewer believes that lichens 

 are the most favorable of all plants for working out problems of distribution. 

 J. M. HoLziNGER (Plant World 4: 185-187. 1901) notes some interesting 

 cases of the local distribution of mosses in southeastern Minnesota, far from 

 their normal range. This occurrence is in the driftless area, and these plants 

 may well be relicts from preglacial days.— H. B. Ayres (U. S, Geol, Surv. 

 Ann. Rept. 21 : 673-689, 1900) has discussed from an economic standpoint 

 the timber conditions of the pine region of Minnesota, An excellent map 

 accompanies the paper.— H. C. Cowles. 



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