ZOOLOGY AND BOTANY, MICROSCOPY, ETC. L99 



spot appears, and branches which have been injured arc the first to show 

 the blackening, which, however, appears naturally in uninjured plants, 

 affecting even the flowers. The author finds that the blackening is due 

 to oxidizing enzymes, of which there are at least two, an oxidase which 

 gives an opalescent blue with gum giiaiac solution, and is destroyed 

 by heat at about 83°-84° C, and a peroxidase which give a deep blue 

 with hydrogen peroxide, and which is destroyed by heat at 86°-87° C. 

 Both enzymes can be destroyed with dilute solutions of citric acid and 

 sodium hydroxide. 



General. 



Identification of Trees in Winter.* — L. H. Scholl, E. C. Cotton, 

 and J. H. Schaffner have prepared keys to the hickories, ashes, and 

 poplars respectively, in the winter condition as regards Ohio species. 

 The characters used are the form, colour and indumentum of the bud, 

 the character of the bud-scales, and the surface characters of the twig, 

 and, in case of hickory, of the bark. There are six species of hickory, 

 seven of ash, and eight of poplar. 



Localised Stages in Common Roadside Plants.f — J. A. Cushman 



describes for a number of common North- American species the various 

 progressive stages towards the adult leaf-form which characterise the 

 seedling, and in the case of perennials, the spring growth, and also the 

 regressive development which occurs on flowering shoots. The species 

 studied include Thalktrum polygamum, Wild Carrot, Wild Indigo 

 (Baptisia tinctoria), Sheep Sorrel, PotenUUa canadensis, Sambucus 

 canadensis, Chenopodium album, Yarrow, and species of Aster and 

 Eupatorium. In Thalktrum and Baptisia, the chief feature is a change 

 in the number of leaflets ; in Rumex, a change in the auricled leaf-base ; 

 in Eupatorium, the presence or absence of the connate leaf -base. 

 Different individuals show variations due to differences in acceleration 

 •of development, which may be due to external or internal causes. 

 Regressive development, seen in localised senescence below the flower, 

 is often more reversionary than stages in the usual seedling. 



Variation of California Plants.^ — E. B. Copeland points out that, 

 while one of the first features of the flora of the mountainous and rather 

 ■dry parts of California which impresses any one familiar with that of the 

 Eastern States and the Mississippi Valley, is the exceeding variability of 

 a great many of the plants, it has yet never been the subject of any 

 particular study. He describes the variation in the leaf-characters — 

 size, margin, base and apex — in a few woody plants comprising several 

 oaks, Rhamnus califomka, Arctostaphylus tomentosa, and species of C'eano- 

 thus and Baccharis. The leaf-variation in a few apparently monstrous 

 ferns is also described. The author then uses his results as a basis for 

 a discussion of the mutation theory in bionomics ; and endeavours to 

 show that there is no foundation for the view that mutations exist as 

 essentially distinct from ordinary variations. 



* Ohio Nat., v. (1905) pp. 269-71. 



t Amer. Nat, xxxviii, (1904) pp. 818-32 (figs, in text). 



% Bot. Gazette, xxxviii. (1904) pp. 401-26. 



