190S] CURRENT LITERATURE 285 



Compositae ofSouthern California.— H. M. Hall^^ has brou.c^ht together our 

 present knowledge of the Compositae of Southern California, an area about the 

 size of Pennsylvania. The 445 species and varieties are distributed as following 

 among the tribes: Eupatorieae (9), Astereae (113), Inuleae (25), Ambrosicac (18), 

 Hcliantheae (34), Madieae (29), Helenieae (86), Anthemideae (19), Senecioncae 

 (25), Cynareae (17), Mutisieae (2), Cichorieae (68). These numbers would be 

 largely increased if the author were not very conservative in his conception of 

 species. As it is, the contribution becomes^a manual of readily recognized forms, 

 which are further brought within easy reach by the numerous well-constructed 

 keys. It is unusual to find in so extensive a contribution that only three new spe- 

 cies have been described, two in Aster and one in Lessingia. However, there is 

 large recognition of varieties, many new ones being proposed; and new combina- 

 tions are frequent. The reduction of numerous names to synonymy may be a 

 service or may add to the confusion, dependent upon the care with which the types 

 were studied. In any event, this type of monograph for so interesting a region is 

 to be commended.— J. M. C. 



Nuclear division in Zygnema.— Escoyez^^ has published the results of cyto- 

 logical studies on Zygnema. The conclusions are as follows: (i) A chromatm 

 network forms chromosomes by gradual concentration. (2) The nucleolus 

 contains no chromatin substance and does not furnish any morphological elements 

 to the chromosomes. (3) The chromosomes are not formed by the fusion of four 



^ anules, as was claimed by :Miss Merkimax. (4) The 

 chromosomes split longitudinally m the metaphase as in typical mitosis. (5) In 

 the telophase the chromosomes first become massed at the poles and then vacuo- 

 lated. The anastomosed structure of the nucleus consists entirely of chromosomes. 

 (6) The nucleolus is not formed by the confluence of chromosomes, but appears 

 quite independent of the chromatin net%\^ork. (7) There is formed no continuous 

 spirem, and the chromosomes evidently keep their individuality. (8) Pyrenoids 

 and chromatophores divide simply by constriction, and the division is independent 

 of that of nucleus. The division of the two pyrenoids does not necessarily occur 

 simultaneously. — S. Yamaxouchi. 



The double leaf trace-— :Miss THOiiAS*° has brought together the facts m 

 reference to the double leaf-trace, so characteristic of the ancient fern and older 



r „-^n ^0.1-0.1 ;« tli^ Hvina rvcads. This condition is 



rm 



.ngiosperms 



is of ver}- frequent occurrence in modem ferns. A phenomenon of such wide 



ggests 



and this 



^8 Hall, H. M., Compositae of Southern CaUfornia. Univ. CaHf. Publ. Bet. 

 3:1-302. pis. i-j, 1907. 



^oEscoYEZ, EuD., Le noyau et la car>^ocinese chez le Zygnema. La CeUuIe 



24:35*^366. pL I. 1907. 



'o Thomas, Ethel X., A theory of the double leaf-trace founded on seedUng 



structure. New Phvtologist 6:77-<>i. figs. 4. 1907- 



