Septembee 25, 1896.] 



SCIENCE. 



433 



An account was given of the state of 

 turgor of seedlings of Vicia faba grown at 

 various temperatures, and an explanation 

 of the high turgor when growth is slow and 

 vice versa. He concludes that the rapidity 

 of growth regulates the amount of turgor 

 present, rather than that the reverse is the 

 case. 



The relation between Thysanella and Polygonella 

 as shown by a hitherto unobserved character : 

 By John K. Small. 



The genus TJiysanella has generally persist- 

 ently and apparently without reason been 

 referred to Polygonum. Besides ample char- 

 acters in the habits and reproductive parts 

 already recorded, the branching in Polygo- 

 nella and Thysanella is internodal, and not 

 nodal, as in all other members of Polygonacece. 



An apparently undescribed species of Primus 



from Connecticut : By John K. Small. 



A relative of Primus maritima growing in 

 the immediate neighborhood with it. The 

 new species differs from the beach plum in 

 habit, leaf form, flower and fruit. 

 The flora of the summits of Kingh Mountain 



and Crowder^s Mountain, North Carolina : 



By John K. Small. 



Two isolated peaks with a moderate alti- 

 tude harboring a local fern (Asplenium 

 Bradleyi) and several members of the AUe- 

 ghenian flora which we should not expect 

 to find there. Their floras are shrubby, 

 with the exception of two perennial herbs ; 

 one fern and a sedge, and about one-half the 

 shrubs on King's Mountain are ericaceous. 

 All the normally large forest trees occurring 

 there are in the form of small shrubs rang- 

 ing from three to six feet in height. 

 Rheotropism and the relation of response to 



stimidus : By F. C. Newcombe. 



Eheotropism is the change in direction of 

 movement or of growth of an organism, in- 

 duced by flowing water as a stimulus. 

 Those organs or organisms that move or 

 bend against the stream are positively rheo- 



tropic, while those moving in the same di- 

 rection with the stream are negatively rheo- 

 tropic. 



It is now shown that the roots of many 

 plants are positively rheotropic, while the 

 roots of others are non-responsive. More- 

 over, the phenomena are marked by char- 

 acters indicating irritability, since there is 

 a latent period preceding the response and 

 an after-effect following the stimulus. 



We need not necessarily assume that the 

 response shows a close biological relation 

 to the stimulus used, since it is certain that 

 in some cases the causal mechanism con- 

 necting stimulus and response may be set 

 in motion by stimuli which are not the 

 usual stimuli calling forth the response. 



Some adaptations of shore plants to respira- 

 tion : By Hermann von Schrenk. 

 A large number of plants growing on the 

 borders of ponds and rivers have developed 

 structures adapting them to more or less 

 aquatic conditions. These modifications are 

 of two kinds, either the development of a 

 mass of spongy tissue serenchyma or the 

 formation of very much enlarged lenticels, 

 termed water lenticels. Decodon verticillata 

 may serve as an example of the first. This 

 plant always develops serenchyma when 

 growing in water. A few cases have been 

 observed where the plant grew in drained 

 ponds, and in those cases no aerenchyma 

 was present. It seems to be well proved 

 that this tissue is simply for respiratory 

 purposes. Sambucus canadensis illustrates 

 the second class. It has a large number of 

 water lenticels developed at its base. These 

 structures, however, are not always present. 

 The same is true of a large number of 

 plants which can grow as well in dry and 

 moist localities. 



On the roots of a number of plants, such 

 as Bidens connata or Pkipatorium perfoliatum, 

 etc., structures occur similar to water len- 

 ticels which serve the purpose of aeration. 



