Ramaley: anatomy of onagraceae. 675 



on the growth of cork, shows how cork is of some taxonomic 

 value, for, in its formation, it is noted as always having its 

 origin in the same cell zone, in any given species. Solereder, 7 

 in 1885, published an extended work on the systematic value of 

 the structure of wood. In Peterson's work, 8 on bicollateral 

 vascular bundles, some little attention is given to the import- 

 ance of this character for purposes of systematic description. 



The pharmacologists have for a long time distinguished vari- 

 ous cellular vegetable drugs by the microscopic appearance of 

 their cross sections. As a rule, however, the descriptions are 

 not sufficiently accurate or minute to serve for the discrimina- 

 tion of closely allied species. In the case of Cinchona barks 

 elaborate classifications have been formulated, based largely 

 upon the size and arrangement of the bast fibres and of latici- 

 ferous vessels. One of the best of these is given by Maish. 9 

 The present writer has not found this classification of any very 

 great value. 



Gibson, 10 in studying the stem anatomy of Selaginella, found 

 marked histological differences in the species; but his group- 

 ing of the species, on these characters— and to this he calls 

 special attention — does not agree with the usual grouping of 

 the systematists. He says (p. 201), "How far comparative 

 anatomy may serve as a basis for a revision of the established 

 classification of the Selaginellaceae, and how far it supports 

 or otherwise, external morphology can only be determined 

 after extended observation on all the members, and not the 

 stem alone." This last statement might be made with equal 

 propriety, concerning those Onagraceae discussed in this 

 paper. 



Bicollateral vascular bundles. — As is well known, the exist- 

 ence of bicollateral bundles was first announced by Hartig, 11 

 who discovered them in Cucurbita. Von Mohl, 12 and numer- 

 ous other writers have contributed to our knowledge of the 

 subject. The following review of researches on bicollateral vas- 

 cular bundles, especially in Onragraceae. will serve to point out 

 the progress of investigation in this direction. 



7. Solereder. Ueber den systematisclien Wertb der Holzstruotur bei don Dieotyle- 



donen. 1885. 



8. Peterson. Ueber das Aitftreten bicollateraler GeMssbiindel u. s. w. Engler's Bo- 



tanlsohe JahrMcher 3:359. 1882. 



9. Maish, J. M. Organic Materia Medica, Ed. VI. 1895. 



10. Gibson. Contributions towards a Knowledge of the Anatomy of the Genus Selagi- 



nella, Spr. -Annals of Botany 8: 133. 1894. 



11. Hartig. Ueber die Querscheidewunde zwischen den ein/.elnen Gliedern der Sieb- 



rohren in Oucurblta pepo.— Bot. Ztg. 18:51. 1854. 



12. Von Mohl. Einige Andeut uiigen fiber fien Bail des Bastes. -Hot . /.tg. 880. 1355. 



