146 ECOLOGY, PLANT GEOGRAPHY [BoT. Absts., Vol. X, 



Publ. Zool. 22: 1-292, PL 1-12, 1 fig. 1920.— The present paper is an exhaustive study, 

 including both the algae and the zooplankton, of the volumetric data, the times and condi- 

 tions of occurrence, as well as the relation to various physical and physiographic features 

 of the region surrounding the locality investigated. There is a very full presentation of data 

 assembled during the investigation. The conclusions are as follows: (1) San Joaquin waters 

 are capable of supporting abundant plankton, and they do so in the vicinity of Stockton; 

 (2) the plankton of the sewage-laden Stockton Channel is distinctly different from that of the 

 river, the number and volume of its animal forms being especially conspicuous as distinguished 

 from the algal dominants of the latter; (3) temperature is, within certain limits, the determin- 

 ing factor in seasonal distribution. This may be by direct retardation of growth and repro- 

 duction in organisms, or by direct influence through food supply and gaseous content of the 

 water; (4) water currents above a moderate speed are distinctly inimical to plankton develop- 

 ment; (5) the peculiar succession of rainy season and dry season has resulted in an autumnal 

 maximum of plankton about Stockton, a condition directly contrary to that of vernal maxima 

 recorded by other observers in other localities; (6) collections taken at intervals of 1 week or 

 more do not furnish a basis for accurate determination of plankton distribution through the 

 year. Daily collections properly taken would probably do so; (7) there is some evidence in 

 favor of the idea that increase of lunar light tends to increase of plankton, especially chloro- 

 phyll bearers; (8) there is evidence to show that fluctuations in amount of plankton occur at 

 various hours of the day; (9) the abundant occurrence of Bacillaria paradoxa, generally 

 listed as a typical brackish water form, is notable. This seems to be one case in which marked 

 departure from a typical chemical environment has not visibly affected structure or behavior. 

 The paper contains lists and notes on the species of the Bacteriaceae, Chlorophyceae, and 

 chlorophyll-containing flagellates collected and studied. — W. A. Setchell. 



949. Alps, H. F., and O. H. Hammonds. Layer measurements of snow on ground near 

 Summit, California. Monthly Weather Rev. 48: 519-520. 1920. 



950. AsTRE, Gaston. Sur la biologie des mollusques dans les dunes maritimes fran^iaises 

 et ses rapports avec la geographie botanique. [On the biology of the molluscs of the maritime 

 dunes of France and its relation to plant geography.] Compt. llend. Acad. Sci. Paris 171 : 678- 

 680. 1920. 



951. Cannon, W. A. Some characteristics of precipitation in arid regions. [Abstract.] 

 Ecology 1:63. 1920. 



952. Douglass, A. E. Evidence of climatic effects in the annual rings of trees. Ecology 

 1: 24-32. 10 fig. 1920. — An attempt is made to correlate climatic effects with the size of 

 tree rings. The main comparisons are made with rainfall during the last 50 years. By means 

 of a periodograph, the ring variations of Sequoias and yellow pines over large areas have been 

 analyzed and found to have numerous corresponding periods or cycles of variability. Further 

 analysis will be based upon a study of mean sensitivity, the difference between each 2 succes- 

 sive rings divided by their mean. This criterion is to be used in selecting materials for a 

 study of past climates as integrated in the growth of tree rings. — Charles A. Shull. 



953. Ferdinandsen, C. Danske Ukrudtsformationer. [Danish formations of weeds.] 

 Nordisk Jordbrugsforskning [K0benhavn] 1920 : 49-67. 1920. — The present article is the author's 

 abstract of his studies on the relations of weeds on cultivated mineral soils. Combining the 

 statistical methods of Raunkiaer and the microbiological soil-testing methods of Christensen, 

 the author details the weed spectra on alkaline and acid soils and gives lists of acidophile, 

 acidokline, amphokline, basokline, and basophile species. It is shown that when cultivated 

 ground is laid out as permanent grass the therophytes gradually are replaced by hemikrypto- 

 phytes and chamaephytes. — Ernst Gram. 



954. Ferdinandsen, C. Traek af Skovbundssvampenes Biologi. [Fungi on forest 

 ground.] Meddel. Foren. Svampekundsk. Fremme [K0benhavn] 1920: 69-82. Fig. 1-3. 1920. — 



