Apeil 8, 1898.] 



SCIENCE. 



497 



place ttemselves at right angles to the direction 

 of the lightr— that is, with their upper surfaces 

 to the window. Leaves and stems, therefore, 

 show sensitiveness characteristic of each. Some 

 stems, however, like those of "Virginia creeper, 

 turn away from light, enabling them to cling to 

 dark walls. Roots, which are generally buried 

 in the soil, rarely exhibit sensitiveness to light, 

 and when they do it is usually to turn from it. 

 If light comes to the organ from two directions 

 it will bend toward the source of the stronger 

 light, and differences which will affect the plant 

 are far more minute than can be detected by 

 the eye." 



In a similar way Dr. MacDougal discusses 

 ' how cold affects plants ' (Chapter VI). After 

 speaking of the general appearance of a frozen 

 leaf, he says (p. 88) : "If now a section is made 

 of a frozen leaf it will be found that the spaces 

 between the cells usually containing air are 

 filled almost solidly with ice crystals. From 

 whence is this ice derived ? " * * * " Protoplasm 

 even in its simplest forms is highly automatic 

 and self- regulating. When the cells of a leaf 

 are subjected to a low temperature they con- 

 tract, and a portion of the water is driven out 

 into the intercellular spaces, where it is frozen. 

 By this provision the proportion of water in the 

 cells is reduced and the danger of ice formation 

 and consequent destruction is averted. If now 

 the temperature is again lowered, an additional 

 amount of water is forced into the intercellular 

 spaces, rendering the cell-solutions still more 

 concentrated, and less easily crystallized into 

 ice." * * " It is thus to be seen that the extru- 

 sion of water into the intercellular spaces is a 

 protective device of the protoplasm." 



It is unnecessary to quote more from these 

 suggestive chapters. These examples will 

 sharpen the interest of every reader of this no- 

 tice, who may be assured that this interest will 

 not flag as he reads the pages for himself. , The 

 book will make an admirable addition to the 

 scientific alcove of every public library. 



Charles E. Bessey. 



The TJniveksity of Nebraska. 



Revision -of the Orthopteran group Melanopli 

 {Acrididse), with special reference to North 

 American forms. By Samuel Hubbaed 



ScuDDER. Proc. U. S. National Museum, 



Vol. 20, pp. 1-421, Plates 1-26. 1897. 



This work by Mr. Soudder deals with a 

 group of acridians of which the Bocky Moun- 

 tain locust and the common red-legged locust 

 are familiar forms. The Melanopli are essen- 

 tially North American, and on account of the 

 number of the species and the variety of the 

 forms present great difficulties to the student. 



A short introduction gives the characters 

 and limitations of the group, and its geograph- 

 ical distribution ; also an interesting note con- 

 cerning the dimorphism in the length of the 

 tegmina, and a statement as to the sources of 

 the material used in the work, acknowledg- 

 ments of aid received, and a few words as to 

 certain details of presentation. 



An elaborate analytical key to the genera is 

 given, and there are also keys to the species of 

 all genera not monotypic. These keys are 

 successful in epitomizing a large amount of 

 close study, and, with the aid of the figures, 

 afford a ready means for the determination of 

 the species ; in all cases, however, the descrip- 

 tions must be consulted for confirmatory data. 



The key to the species of Melauoplus (pp. 

 124-139) is so long as to suggest that a separate 

 tabulation of the groups, designated as series, 

 and of the species under each group, would 

 have been more useful. 



The generic and specific descriptions are 

 given with the detail characteristic of Mr. 

 Scudder's work. Thirty genera are recognized 

 and of these eighteen are described as new, of 

 North American species 208 (113 new) are de- 

 scribed. An analytical key to the Old World 

 species of Podisma with brief notes, including 

 descriptions of two new species, is also given. 



The material upon which these genera and 

 species are based has in most cases been ample, 

 more than 8, 500 specimens having been studied ; 

 of the 208 species but two are unknown to 

 Mr. Soudder ; 31 species are known from one 

 sex only and 21 species from uniques. The 

 females outnumber the males, 4,596 to 3,911, 

 or, stated differently, in 96 species the females 

 are the most abundant, in 75 species the males ; 

 in 37 species the numbers are the same. The 

 bibliography and geographical distribution are 

 given in admirable detail. 



