i9i 2] CURRENT LITERATURE 175 



the three systems, and hence includes almost all the annual plants. Few of 

 these annuals penetrate the soil deeper than 20 cm., and most of the lateral 

 branches are less than half this distance from the surface. Competition is 

 evident between the various members of the generalized type, and also between 

 them and those of the first specialized class. The best development of root 

 systems is found in the summer annuals, due to more favorable vegetative 

 conditions, and particularly to more favorable soil temperature during that 

 portion of the year. 



The details of root development in the various species are illustrated by 

 many photographs and drawings, while the detailed descriptions contain many 

 interesting facts concerning the different plants. — Geo. D. Fuller. 



Chromatophores and chondriosomes. — Forenbacher 14 has made a 

 study of the origin of chloroplasts and leucoplasts in the stem and root of 

 Tradescantia virginica, the object of which is to show the origin of these struc- 

 tures from chondriosomes (filamentous mitochondria). Beginning with the 

 fully formed chloroplasts of the stem cortex and leaves and proceeding toward 

 the tip, he finds a complete gradation between the fully formed chloroplasts 

 and the chondriosomes. The intermediate forms present themselves as dumb- 

 bell and granular structures which gradually pass over into the chromatophores. 

 Similar gradations are found between the chondriosomes (mitochondria) of the 

 root tip and the leucoplasts. This work thus confirms the results of Pexsa 

 and Lewitsky and those of Guilliermond on the origin of the chloroplasts 

 from mitochondria (chondriosomes). 



Some doubt is justified of the efficiency of the methods employed for 

 demonstrating the chondriosomes of plant cells. Meves, for example, found 

 these structures in the tapetal cells of Nyrnphaea, but not in the spore mother 

 cells, in which, however, by suitable methods they may be shown to be very 

 numerous. The reason was the small power of penetration of the fixing 

 fluid, which did not reach the deeper tissues before the mitochondria had 

 undergone change or disappeared. In eliminating acetic acid wholly from 

 his fixing fluid, Forenbacher has diminished its already slight power of pene- 

 tration. His figures are not convincing, for the structures labeled as chondrio- 

 somes do not conform in shape or number to the usual condition in rapidly 

 dividing cells of higher plants. It is quite possible that his young chloroplastids 

 do not belong to the category of mitochondria (chondriosomes) at all. — R. R. 

 Bensley. 



Vascular anatomy of Salicales.— Miss Holdex 15 has investigated the 

 position of Salicales on the basis of the vascular anatomy of the North American 



14 Forexbacher, Aurel, Die Chondriosomen als Chromatophorenbildner. Ber. 

 Deutsch. Bot. Gesells. 29:648-660. pi. 25. 191 1. 



15 Holden, Ruth, Reduction and reversion in the North American Salicales. 



Anil. Botanv 26: t6c-t7i> /i/c on it Tm? 



