Botany 123 



indefinite upper limit, and embracing diverse structural types from fresh-water 

 aquatics to xerophytic dune plants. 



The environmental factors, whose influences on the distribution of the plants 

 of this harbor are considered, are the following: (1) Substratum, including its physi- 

 cal character, its mobility, and its capacity for drainage and aeration. (2) Water 

 currents, including the dispersal of spores, seeds, and shoot-fragments, the me- 

 chanical injury of the plants, the shifting of soil, and the favoring of interchange 

 between the plant and the surrounding water. (3) The submergence and exposure 

 due to tides, which affect the aeration and transpiration, the light supply, the ex- 

 posure to rain at low-water, and the salinity of the soil water at high levels. 

 (4) The salinity of the soil water and the submerging water including especially 

 the changes in density during the course of the tide near the numerous fresh-water 

 streams. (5) Temperature of the water including daily and seasonal changes. 



The important general conclusion is reached, as a result of observations here 

 and at other points on the Atlantic Coast, that the vertical range of a plant common 

 to two localities with different ranges of tide will be found exactly proportional in 

 each place to the local range of tide. 



No. 209. RICHARDS, HERBERT M. Acidity and Gas Interchange in Cacti. Octavo, 

 107 pages, 6 figures. Published 1915. Price $1.00. 



This paper presents the results of a somewhat detailed study of the behavior 

 of the acidity and gas interchange of Opuntia versicolor, together with some data 

 from other cacti. The section on acidity determinations embodies a consideration 

 of the periodicity of acid formation and disappearance, with experimental data 

 and discussion of the various external factors which influence the acid content of 

 the tissues. Following this is a chapter on the respiration of cacti as determined 

 by the Pettenkofer method in which especial attention is called to the lag in 

 response of the rate of carbon-dioxide evolution with changing temperatures. The 

 third part of the paper treats of gas interchange in connection with the determina- 

 tion of what is commonly termed the respiratory quotient. The effect of light, 

 darkness, increased or diminished oxygen supply, rising and falling temperatures, 

 wounding, etc., are described. The paper closes with a short consideration of the 

 question of respiration in general, especially in connection with the peculiar 

 phenomena presented by the cacti. 



No. 218. STOUT, A. B. The Establishment of Varieties in Coleus by the Selec- 

 tion of Somatic Variations. Octavo, 80 pages, 4 plates, 29 figs. Pub- 

 lished 1915. Price $2.00. 



This study pertains to the frequency, the permanence, and the nature of somatic 

 variations involving leaf-shape and variegation in Coleus, and to an analysis of 

 such phenomena with reference to the expression and the inheritance of char- 

 acters. A single variety of Coleus propagated vegetatively in pedigreed cultures 

 through six generations (833 plants) developed two types of changes: (1) fluctu- 

 ations, and (2) mutations, giving a total of 16 distinct color patterns and a type 

 of plant with periodically laciniate leaves. Selection was effective in maintaining 

 15 color patterns remarkably constant in vegetative propagation; these exhibited, 

 however, further variations. 



The phenomena associated with the appearance and the subsequent behavior of 

 the different variations are quite similar to variation and mutation in seed progenies 

 and to alternative inheritance in hybrid progenies. The results show that in Coleus 

 asexual and sexual reproduction are not fundamentally different in respect to the 

 extent and range of variation. Furthermore, the phenomena illustrate, in the de- 

 velopment of green, yellow, and red coloration, the behavior of metidentical 

 qualities and show equally well that the distribution of colors in patterns is due to 

 inter-cellular and inter-tissue relations and is without doubt due to physical and 

 chemical processes quite analogous to the Liesegang precipitation phenomena. 



