1919] AGRICULTURAL BOTANY. 429 



the make-up of the biological complex in any given region, and to obtain com- 

 parable expressions for the results of climatic and other factors as recorded in 

 the life forms developing in any locality under natural conditions. 



Statistical studies on vegetative formations, C. Raunki.er {K. Danslce 

 Vidensk. Sclsk., Biol. MeddeL, 1 (1018), No. 3, pp. 80).— This contribution em- 

 ploys the term foi-mation (for a fundamental unit to be used as a basis for 

 classificatiou and discussion of vegetations) in a way to cori-espond somewhat 

 to the term species in classification of individual plants. It defines the term as 

 a growth somewhat homogeneous as regards its composition and general charac- 

 ter determined by the conditions of the environment, being a biological expres- 

 sion of such conditions. Several main sections deal with the degree of fre- 

 quency of species as applied to fioristic characterization of plant formations, 

 the law of distribution of frequencies, utilization of the degree of frequency 

 as a biological characteristic of formations, and the degree of covering of the 

 soil by species as applied to physiognomic characterization of formations. 



The theory of limiting factors, W. H. Brown (Philippine Jour. Sci., Sect. C, 

 13 (1918), No. 6, pp. 345-351, fig. i).— This is a critical review of Blackman's 

 theory of limiting factors (E. S. R., 18, p. 923 ; 24, p. 533) and of facts and views 

 contributed by other authors. 



The origination of ascidia under quasi-experimental conditions, F, E. 

 Lloyd (Proc. and Trans. Roy. Soc. Canada, 3. ser., 11 (1917), Sect. IV, pp. 71-80, 

 ftgs. 4). — The author describes the results of abnormal development in a large 

 number of seedlings of Gossypiuni herbaceum, supposedly due to the mechanical 

 pressure resulting from disharmonious growth. The plants v/ere allowed to 

 grow for over a year in 3-in. pots, during much of which time they were either 

 dormant or growing under higher temperatures or more abundant watering than 

 usual, finally settling down to a balance of activities scarcely sufficient to keep 

 them alive. Such buds and shoots as formed were highly abnormal as regards 

 form, the leaves produced remaining juvenile in character. It appears probable 

 chat the tendency to form ascidia is an abnormal expression of an attempt to 

 form separate lobes. The malformations obsei-ved are not supposedly identi- 

 cal with tomosis. 



Alternate shrinkage and elongation of growing stems of Cestrum noc- 

 turnum, W. H. Beown and S. F. Trelease (Philippine Jour. Sci., Sect. G, 13 

 (1918), No. 6, pp. 353-360). — From among a number of rapidly growing plants 

 in Manila which wilt during a comparatively dry summer day, the authors 

 chose 2 plants of C. nocturnum as material for the study of this phenomenon. 

 It was found that the shoots wilt regularly, frequently decreasing in length 

 owing to excessive transpiration on every comparatively dry day, but regain 

 their original length in the evening or night, after which they elongate rapidly. 



Algological notes. — III, A wood-penetrating alga, Gomontia lignicola n. 

 sp., G. T. Moore (Ann. Missouri Bot. Oard., 5 (1918), No. 3, pp. 211-224, pis. 3).— 

 The author reports a study of an alga occurring partly on and partly within 

 the tissues of a yellow-pine board submerged in fresh water. The organism is 

 described as G. lignicola n. sp. Apparently the penetration of the wood was not 

 a consequence of disintegration. 



A study of stomata, L. Rehfous ([Trav.'\ Inst. Bot. Univ. Qentve, 9. ser., 

 No. 6 (1917), pp. 110, figs. 135; abs. in Rev. Gin. Bot., 30 (1918), No. 359, pp. 366, 

 367).. — This is a detailed account of studies on stomata in a large number of 

 plant families, emphasis being placed on such minute details as number, arrange- 

 ment, or cutinization of cells in relation with stomata. Desciiptions are given 

 of new stomatal types in Polypodium, Platycerium, Cycas, and Casuarina. A 

 practical phase of the work is presented in connection with a possibility of de- 

 tecting adulteration in such articles of commerce as drugs and tea. It is 



