No. 1. July, 1920] ECOLOGY, PLANT GEOGBAPHT 



Crambe maritima, and Honch nya peploides, possibly because they occur well up on the beach 

 where the salt percentage is low. Eigher pressures were found in ^i» rgularia salina, 



timus, and Armaria elongata. The highest pressure was found in Atriplex latifoliwm, 

 which explains the presence of this species down to the littoral zone. The permeability of 

 Beveral halophytes for NaCl and other salts was determined by the Fitting method, and was 

 found to be so slight as scarcely to be measurable; this slight permeability may he regard<d 

 as a high tide adjustment, preventing plants from taking up too much salt. The power of 

 keeping down salt accumulation also may determine how far down toward the sea a plant 

 may extend its habitat. The transpiration of halophytes was found uniformly to he less 

 than that of mesophytes. Sun and shade forms of Scdum maximum and Solanum dulcamara 

 have about the same osmotic pressure. Atriplex lati folium has two forms, a pale yellowish 

 green littoral form, and a deep green supra-littoral form; the latter has twice as many stomata 

 as the former, and the transpiration is proportionally greater. — //. C. Cowles. 



24 1. MacDougal, D. T., H. M. Richards, and H. A. Spoehr. Basis of succulence in 

 plants. Bot. Gaz. 67: 405^116. May, 1919. — A Castilleja native to the region about Carmel, 

 California, includes two habitat forms, -genetically identical, a thin-leaved forest form and 

 a fleshy-leaved shore form. The thin leaves show an acidity double that of the fleshy type, 

 and have a greater dry weight. The fleshy leaves present swelling reactions similar to those 

 of sections of Opuntia, indicative of cells high in pentosans or mucilages. The thin leaves 

 swell more in acid than in alkaline solutions. Differences in the swelling reactions of dried 

 leaves of both kinds are to be ascribed to the adsorption of the contained acids and salts of 

 different amounts in the two cases on cell colloids, high in pentosans in one case and hence 

 presenting characteristic coagulatory effects. The reduction of the water content of the 

 cell below a certain point results in the conversion of polysaccharides, which do not show a 

 high inhibition capacity, to pentosans, which mixed with nitrogenous substances have an 

 enormous hydration capacity. Succulence, therefore, may be a direct result of aridity. High 

 acidity, contrary to general impression, may not be taken as a result of succulence. It is 

 more probable that succulence may develop only in plants which have a carbohydrate 

 metabolism characterized by large acid residues. — H. C. Coivles. 



245. Magrou, J. L'immunite dans la symbiose. [Immunity in symbiosis.] Ann. Inst. 

 Pasteur 32: 37^7. PL 1918— See Bot. Absts. 2, Entry 193. 



246. McAtee, W. L. Summary of notes on winter blooming at Washington, D. C. Proc. 

 Washington [D. C] Biol. Soc. 32: 129-132. 1919.— Due to the mild winter of 1918-19 unusual 

 flowering phenomena occurred in the neighborhood of Washington, D. C. The author divides 

 these phenomena into four groups, viz. : Autumnal flowering, late flowering, early flowering, 

 and casual flowering. Lists are given of the plants in wdiich such phenomena were found. — 

 J. C. Gilman. 



247. McDougall, W. B. The classification of symbiotic phenomena. Plant World 21: 

 250-256. Oct., 1918. — Symbiosis is defined as the living together of dissimilar organisms, and 

 symbiotic phenomena classified as disjunctive or conjunctive. Each of these two main 

 divisions is subdivided into social and nutritive. And nutritive symbiosis, whether disjunc- 

 tive or conjunctive, is further classified as antagonistic or reciprocal. Examples are cited. — 

 Chas. A. Skull. 



248. Miehe, Hugo. . Anatomische Untersuchung der Pilzsymbiose bei Casuarina equi- 

 setifolia nebst einigen Bemerkungen fiber das Mykorhizenproblem. [Anatomical studies on 

 fungal symbiosis in Casuarina equisetifolia with some remarks on the mycorhiza problem.] Flora 

 11-12: 431-449. 1 pi., 2 fig. 1918. — The roots of Casuarina equisetifolia, growing on coral 

 islands near Java, bear structures very similar to the root tubercles of the alder. These tu- 

 bercles were found to consist of closely compacted masses of numerous, freely-branching, 

 shortened rootlets, certain of the cortical cells of which contain the hyphae of a fungus. The 

 author designates these tubercles "Rhizothamnien," and ascribes their formation to the in- 



