12 ECOLOGY, PLANT GEOGRAPHY [BoT. Absts., Vol. VIII, 



tral soils. Among the Orchidaceae, the northern species seemed to attain their greatest de- 

 velopment in circumneutral soils, i.e., neutral or only weakly acid or alkaline soils, while 

 most of the southern species apparently preferred more acid soils. — The paper concludes 

 with a list of plants studied, other than those of the above two families, which proved to be 

 oxylophytes, and a list of those which were found to be calcicoles. — James P. Poole. 



93. Wherry, Edgar T. The soil reactions of certain rock ferns — I. Amer. Fern Jour. 10: 

 15-22. 1920. — The author gives a table, "Classification of Rock Fefns on the Basis of Soil 

 Reaction," listing 7 acid soil plants and 18 calcareous soil plants. He then discusses 7 indi- 

 vidual species representing 4 genera.— F. C. Anderson. 



STRUCTURE, BEHAVIOR 



94. Jaqtjes, H. E. Some phenological records of spring flowering plants of Henry County. 

 Proc. Iowa Acad. Sci. 25:413-415. Fig. 162. 1920. — Dates of first flowering of twenty 

 species appearing in March, April, and May, 1915-1918, at Mt. Pleasant, Iowa,' are shown 

 in a table. Six species are shown on a graph. In 1916 Acer saccharinum, Phlox divaricata, 

 and Berberis vulgaris bloomed later than in any other year. But Sanguinaria canadensis and 

 Acer negundo bloomed latest in 1917. — H. S. Conard. 



95. Schmidt, Wilhelm. Die Verbreitung von Friichten durch die Luftbewegung. [The 

 distribution of seeds by air currents.] Naturwissenschaften 7: 810-812. 1919. — Formulae 

 are developed whereby the distances to which winged seeds and pollen may be carried by 

 the wind can be determined. — Orton L. Clark. 



96. Stevens, O. A. Notes on species of Halictus visiting evening flowers (Hyn.). Ento- 

 mol. News 31 : 35-44. 1920. — Some observations on four species of bees visiting evening flow- 

 ers, particularly primroses, are recorded. One species is new; this one and two others are 

 especially adapted to collecting pollen from the Onagraceae, due to a sparseness of the scopa 

 which makes possible the adhesion of the pollen mass. Observations on the opening of the 

 flowers and the visits of the bees are recorded for Megaptermium missouriense, Allionia hirsuta, 

 Onagra strigosa, Anogra pallida, and Gaura coccinea. These bees fly about the flower buds 

 before any sign of opening is visible; at the first small opening they force their way in, one or 

 two visits stripping the flower of its pollen mass. A group of Onagra plants observed at 

 intervals showed that most of the flowers open at 9:00 p.m., although some were found to 

 open later in the evening. — Wanda Weniger. 



97. Weaver, J. E. The ecological relations of roots. Carnegie Inst. Washington Publ. 

 286. 128 p., 30 pi., 58 fig. 1919. — The root habits of about 140 species of dominant and 

 subdominant shrubby and herbaceous plants occurring under a wide range of environmental 

 conditions and studied in the field are described and in part figured by habit photographs 

 and root maps. The communities represented in the research include the chaparral of south- 

 eastern Nebraska, the prairies of eastern Nebraska and of southeastern Washington, "the 

 plains association and sandhill subclimax of Colorado, and the gravel-slide, half-gravel- 

 slide, and forest communities of the Rocky Mountains of Colorado." With the description 

 of the root systems of each community is given an account of the temperature, precipitation, 

 evaporation, wind movements, and notes on the soil conditions, including the moisture con- 

 tent. — In the prairies of eastern Nebraska more than half of the plants studied have roots 

 which penetrate to a depth exceeding 5 feet, with a maximum penetration of 13-20 feet. 

 The roots exhibit a condition of layering with accompanying reduction of competition of 

 contiguous species for soil moisture. The soil is loess and glacial drift, and the water con- 

 tent of the upper 4-5 feet may be so reduced that none is available for plant growth. About 

 71 per cent of the rainfall occurs during the growing season. The mean summer tempera- 

 tures are high and the mean humidity is often low. The wind averages about 70 miles per 

 day. — The plants of the prairie community of southeastern Washington are not so deeply 

 rooted as are those of the Nebraskan prairies. Out of a total precipitation of 21 inches annu- 



