690 



SCIENCE. 



[X. S. Vol. XVIII. Xo. 405. 



unfertilized ova. In order to supply the de- 

 mand for terrapin many were imported from 

 the southern states, including representatives 

 of two distinct and, as yet, undescribed spe- 

 cies. It had been thought that these might 

 be crossed with the Chesapeake terrapin, but 

 as none were kept a sufficient length of time, 

 four years, after importation no results had 

 been obtained. Owing to close hunting and 

 disregard of the laws, the Chesapeake terrapin 

 was threatened with extermination, and the 

 simplest remedy suggested was to forbid the 

 sale of the larger terrapins, since these were 

 invariably breeding females. 



F. A. Lucas. 



THE TORREY BOTANICAL CLUB. 



At a meeting of the club held at the Bo- 

 tanical Garden on October 28 the following 

 scientific notes and papers were presented: 



Dr. MacDougal called attention to the ab- 

 normal fall blooming of certain plants. In 

 one case mentioned the spring flowering of 

 certain plants was retarded till fall, owing to 

 the presence of a mass of ice, this being a 

 case of retarded development. He exhibited 

 plants with flowers now open that should not 

 normally open till next spring, this being 

 accelerated development caused by the pre- 

 vailing climatic conditions. 



Dr. Britton exhibited two forms of the com- 

 mon marsh mallow, one with pink flowers, 

 the other with white flowers with a crimson 

 center. The first is the well-known Hihiscus 

 Moscheutos L. The second form is not un- 

 common in various localities, but has been 

 considered merely a color variation. Recently 

 it has been observed that the fruits of the two 

 forms are very different, showing that they 

 should be considered distinct species. Draw- 

 ings of the fruits were exhibited. No name 

 has as yet been proposed for the white-flowered 

 form. 



Dr. Livingston spoke on the ' Influence of 

 Osmotic Pressure on the Cell.' One of the 

 widely accepted theories of the action of os- 

 motic pressure is that it is comparable to gas 

 pressure. It can only act, however, in the 

 presence of water. Soluble salts tend to dif- 



fuse throughout a given volume of water just 

 as gases do in a confined space. In cellular 

 tissues there is no break in the water connec- 

 tion, since the cell wall is permeable by water 

 and by the salts dissolved in it. The proto- 

 plasmic lining of the cell is, however, only 

 semi-pei-meable, since it allows the passage 

 of some substances while preventing that of 

 others. When living cells are transferred 

 from a thin dilute medium to a denser one 

 the tendency is for them to lose part of the 

 water they contain. The cell contents thus 

 become more or less shriveled. Conversely, 

 when a cell is transferred to a more dilute 

 medium it swells and becomes more turgid. 

 Strong solutions tend to check vital activity. 

 Eemoval to a dense medium often materially 

 alters the form of growth of an organism, the 

 tendency being to assume short thick forms 

 in the dense medium and longer and more 

 slender forms in the dilute ones. With dif- 

 ferent substances that are not poisonous the 

 cell seems to give the same response when a 

 strength of each is used that would exert the 

 same osmotic pressure, showing that it is the 

 pressure and not the character of the sub- 

 stance that produces the effect. The extraction 

 of water from the cell means the concentra- 

 tion of the solution of all the various salts 

 and other dissolved substances that are con- 

 tained in it. Varying strengths of the same 

 salt are known to affect the growth of plants 

 very diversely, and this suggests an interesting 

 field for further investigation. 



The paper brought out an interesting dis- 

 cussion as to the probable effect on the 

 aquatic vegetation of a gradual change from 

 fresh to salt-water conditions. 



Mr. Earle discussed ' Generic Limits among 

 the Agaricaceffi.' He called attention to the 

 artificial character of the genera that are now 

 recognized and the unnatural grouping of 

 species that resulted from the use of only two 

 or three characters as the basis of genera. A 

 more natural grouping would require that the 

 sum total of all the characters should be con- 

 sidered in defining genera. 



F. S. Earle, 

 Secretary. 



