NOTES ON KELPS. 47 



able to examine an authentic specimen of this plant, and 

 through the kindness of Dr. Anderson he has obtained also 

 several specimens more, and as a result of careful study and 

 investigation feels sure that it cannot be separated generi- 

 cally from Dictyonenron. The reticulations on the blade, 

 the short, thick stipe with lateral branched rootlets point 

 unmistakably toward Dictijojienron. Furthermore there is a 

 specimen in the University Herbarium at Berkeley, collected 

 by Mr. M. A. Howe at Pacific Grove in July, 1892, (cf. PI. I) 

 with reticulations and a partial " midrib," which is beginning 

 to split longitudinally at the base, showing it to be a true Dic- 

 tyo7ie7cron. Several of Dr. Anderson's specimens, also provided 

 wath undoubted "midribs," have their blades borne upon 

 dichotomously branched stipes and give additional evidence 

 that the Costaria reticulcda is a Dictyonenron. 



But no species of Dictyonenron has been described as hav- 

 ing a midrib such as is credited to Costaria reticulata. An 

 examination of Mr. Saunder's specimen shows, however, that 

 this middle structure is not a real rib. It is described as 

 varying in width from a little over a quarter of an inch to 

 two inches and as being about '• twice the thickness of the 

 body of the plant." The varying width is well illustrated 

 by the specimens in the writer's possession, but he does not 

 fiind the thickness as represented. In the middle of the so- 

 called midrib of Mr. Saunder's specimen the thickness is that 

 of the ordinary unmodified portions of the frond but at the 

 edges it is thicker and the writer finds that the "midrib " is 

 simply a central portion of the blade, free from reticulations 

 between two prominent longitudinal ribs, such as are not un- 

 common in specimens of Dictyonenron Californicum. For 

 on examining a number of specimens of D. Californicnm 

 this central space between two longitudinal ribs is often 

 found and sometimes it is perfectly plane, sometimes reticu- 

 lated, and sometimes plane below and reticulated above (cf. 

 PI. I). Kuprecht says in his original diagnosis (loc. cit.; 80); 

 "nervo longitudinali (iuterdum duplici) folium usque ad 

 apicem permeante." 



This character, then, striking as it is in some specimens, 

 does not seem to be either constant or characteristic and 



