760 



SCIENCE 



[N. S. Vol. XLIV. No. 1143 



tweeH chaparral and forest, and 6°.0 between 

 chaparral and open, the differences being greater 

 in summer and least in winter. 



Eighty per cent, of the precipitation reaches the 

 ground under chaparral and seventy-two per cent, 

 under the forest, much more water reaching the 

 ground from snowfall under chaparral than forest. 

 A difference of 5 per cent, exists between open and 

 areas under cover, though there is but slight dif- 

 ference between the types of cover. Evaporation 

 in the forest is 85.2 per cent, that of the open, 

 while the chaparral evaporation is but 47.2 per 

 cent. 

 Plant Succession in Badlands: Frederic E. 



Clements. 



An account of the revegetation of the highly 

 eroded clays and shales, known as Badlands. The 

 areas considered are the Oligocene-Miocene depos- 

 its of the Hat Creek Basin in Nebraska, and of 

 the "White Biver in South Dakota, the Eocene of 

 the Little Missouri in North Dakota and Mon- 

 tana, Miocene volcanic deposits in Wyoming, and 

 the Mancos Shales of Colorado, Wyoming, Utah 

 and New Mexico. In the last, the climax is the 

 Atriplex-Artemisia formation of the Great Basin 

 region. In all the others, the climax is the prairie- 

 plains grassland, except in the Black Hills proper, 

 where it is the Pinus ponderosa forest. The soil 

 water of the Mancos Shales is saline, and the suc- 

 cession type is the halosere, consisting of halo- 

 phytes and terminating in a sage-brush climax, or 

 rarely in juniper-pifion woodland. In all the Ter- 

 tiary Badlands of the Great Plains region, the 

 fine-grained compact soil, the steep slope and the 

 low but torrential rainfall make xerophytie suc- 

 cession, as represented by the xerosere, typical. 

 The hydrosere and halosere are relatively rare, 

 while subseres are especially favored by the na- 

 ture of the soil. The climax is usually reached in 

 the Stipa-Agropyrum prairie association. In drier 

 regions, the climax is the Bulbilis-Bouteloua short- 

 grass association, and in wetter ones, the Pinus 

 ponderosa consociation. 

 A Summary of Bog Theories: George B. Bigg. 



A discussion of the character and occurrence of 

 sphagnum bogs, and a presentation of the theories 

 that have been advanced to account for the 

 xerophily of bog plants, the possible sources of 

 toxic substances in bog water, and the manner in 

 which these substances influence the activities of 

 plants. 

 Vital Statistics of the Yellow Pine through an 



Altitudinal Gradient of Climatic Conditions: 



Forrest Shreve. 



Vital statistics have been secured for Pinus 

 arizonica at elevations of 6,000, 7,000, 8,000 and 

 9,000 feet on south-facing slopes in the Santa 

 Catalina Mountains, Arizona, and on north-facing 

 slopes at 6,000 and 7,000 feet. The number of 

 adult trees (10 em. and over) per unit area de- 

 creases with decrease of altitude, except on the 

 south-facing slopes at 6,000 feet. The total vol- 

 ume per unit area decreases with decrease of alti- 

 tude, the exceptional stand at 6,000 feet being com- 

 posed of a relatively large number of small trees. 

 The number of seedlings and smaller trees bears no 

 relation to altitude on the areas examined. Curves 

 were exhibited showing the rate of growth at the 

 four altitudes. 

 The Influence of Environmental Conditions in the 



Origin of a Narrowly Localized Race of Mice: 



Francis B. Sumner. 

 The Distribution of Pocket Gophers in California: 



Joseph Grinnell. 

 On Some Varieties of Thais {Purpura) lapillus 



and their Belation to the Environment : Harold 



S. COLTON. 



On account of its abundance and great variation, 

 Thais (Purpura) lapillus forms a very favorable 

 material for a study of some of the conditions of 

 life on the rocky shores of the New England coast. 

 Over twelve thousand shells were collected and sorted 

 from sixty-seven localities in the neighborhood of 

 Mount Desert Island, Maine. Thais is found in the 

 rock association and the boulder association of the 

 littoral formation wherever its food, Balanus, the 

 barnacle, and Mytillus, the mussel, is found. The 

 environments were classified according to the size 

 of the waves on the beach and on the color and 

 character of the rocky substratum. A study of 

 the varieties showed that (1) in the surf and in 

 the sheltered harbor the snails of a given age 

 were smaller and darker than those found in the 

 bays. More were also apt to be lamellated in the 

 surf or harbor than in the bays; (2) light forms 

 are apt to be found on light-colored rocks, but 

 there is no great correlation between yellow snails 

 and yellow rocks or banded snails on banded 

 rocks; (3) there are other factors which act on a 

 whole region irrespective of the wave action or 

 substratum. An example of this was found in 

 comparing the number of lamellated forms in the 

 Somes Sound region with the Blue Hill Bay re- 

 gion adjoining. In the former, whether in harbor, 

 bay, or surf, lamellated forms are rare (6 per 

 cent.). In the latter they are common in the har- 

 bors, as much as 96 per cent, in some, absent in 

 the bay but common (17 per cent.) in the surf. 



