278 BOTANICAL GAZETTE [march 



established by means of the open water-suffused stomata. This would account 

 for the effectiveness of the film at night and for its lack of effectiveness with 

 Cyperus with its very narrow stomata. The authors state that there are 

 difficulties in the incipient guttation explanation as applied to excised leaves. — 

 Wm. Crocker. 



• Turgor movements. — Blackman and Paine/' by use of a special con- 

 ductivity cell, have studied the conductivity of the liquid extruded from the 

 lower half of the excised pulvinus of Mimosa pudica due to the shock stimulus. 

 The shock response gives an increase in conductivity, but not nearly enough 

 to attribute the contraction to increased extrusion of solutes. They beUeve, 

 therefore, that the contraction is due to a sudden condensation of solutes within 

 the pulvinal cells of the lower half of the pulvinus. They consider the con- 

 ductivity method far superior to the plasmolytic method used by previous 

 authors, for it answers directly the amount of movement of solutes. Under 

 certain conditions they get autonomic movements of this organ similar to those 

 of the leaflets of Desmodium gyrans. A slow rise of temperature up to 50° C. 

 shows little increase in exosmose of electrolytes from this organ. The increase 

 of permeabiUty at higher temperatures seems to be due to lethal irreversible 

 changes. — ^Wm. Crocker. 



Alternation of generations in Padina. — Padina variegata, one of the 

 Dictyotaceae, is abundant at Beaufort, North Carolina, where it has been 

 studied by Wolfe.^" Sperms, eggs, and tetraspores are borne on 3 separate 

 plants which look aUke in the vegetative condition, but which are easily 

 recognized during reproduction. Tetraspores give rise to only male and female 

 plants in approximately equal numbers, so that sex is probably predetermined 

 during the reduction division in the tetraspore mother cell. Fertilized eggs 

 produce only tetrasporic plants, so that there is an alternation of sporophyte 

 and gametophyte generations. Eggs often germinate without fertiUzation, 

 but plants of such parthenogenetic origin do not mature. It would be interest- 

 ing to know the chromosome numbers, especially in the parthenogenetic plants, 

 and we hope that Wolfe, who is familiar with the cytological technique of the 

 algae, will investigate this phase of the problem. — C. J. Chamberlain. 



The luminous moss. — Tod A" has made a physiological study of Schistostega 

 osmundacea, the so-called luminous moss, his material having been obtained 

 from a cave in Japan. He found the optimum intensity of light as well as the 

 minimum and maximum intensities in terms of Bunsen's unit. In a dark place 



'9 Blackman, V. H., and Paine, S. G., Studies in the permeability of the pulvinus 

 of Mimosa pudica. Ann. Botany 32:69-85. 1918. 



'" Wolfe, J. J., Alternation and parthenogenesis in Padina. Jour. Elisha Mitchell 

 Scientific Soc. 34:78-109. 1918. 



'^ ToDA, Viscount Yasumochi, Physiological studies on Schistostega osmundacea 

 (Dicks) Mohr. Jour. Coll. Sci. Tokyo 4o:no. 5. pp. 30. pis. 2. 1918. 



