ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 601 



was measured by plasmolysis in potassium nitrate and glucose 

 solutions. Measurements were made on straight, bending, bent and 

 unbending tentacles. The osmotic concentration in the cells on the 

 abaxial side of the stalk, in the growing region, was found to 

 diminish during bending ; no change was observed on the adaxial 

 side. The decrease in osmotic concentration is accounted for by the 

 increase in volume of the cells, and is therefore considered an eilect 

 and not a cause of their elongation. There is no indication that 

 changes in permeability occur. The elongation is produced by a 

 decrease in the elasticity of the cell-walls, and is later fixed by growth. 

 The movement of tentacles is therefore brought about by the same 

 mechanism found in geotropically reacting organs, where a decrease has 

 been observed in the osmotic concentration in the cells whose growth 

 causes bending. 



Similarities between hydrotropic reactions and autotropic unbending 

 of tentacles and of geotropically bent roots indicate that the growth on 

 the concave side which brings about the unbending is a response to 

 changes resulting from the difference in osmotic concentration present 

 during bending. As in hydrotropic reactions, growth takes place on the 

 side with the higher osmotic concentration. 



CRYPTOGAMS. 



Pteridophyta- 



(By A. Gepp, M.A., P.L.S.) 



New Investigations of Athyrium and Botrychium.* — F. K. 



Butters begins a series of critical studies of some of the North American 

 ferns which have a very wide and somewhat anomalous distribution. 

 Being of opinion that too much reliance has been placed on such super- 

 ficial characters as details in the form and cutting of the fronds, he has 

 deemed it wise to study such technical characters as the size, form and 

 sculpture of the spores, and details of the structure of the sporangia, 

 sori, indusia and scales, in the hope of finding characters of a more 

 stable nature. This investigation has led to the separation of species 

 and varieties in the case of several common groups of ferns, and in other 

 cases to the recombination of forms supposed to be distinct. And the 

 result is to make the ferns agree more with the laws of distribution 

 applicable to the phanerogams. 



I. The first study treats of the genus Athyrium. Among the con- 

 clusions reached are the following : (1) In the Eastern United States 

 and Canada there are two distinct species of Lady Ferns, neither of which 

 is conspecific with A. FiUx-femina of Europe ; one, A. asplenioides, is 

 prevailingly southern in its distribution ; the other, A. angustum, is 

 prevailingly northern. (2) The plants of the north-west are conspecific 

 with the European plant, some forms differing in minor points. (3) The 

 Cahfornian plants and those of the Southern Rocky Mountains differ 



* Khodora, xix. (1917) pp. 169-216 (] pL). 



Dec. 19th, 1917 2 s 



