12 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



upon the greater value of certain characters as specific 

 distinctions and the less value of others. The more variable 

 characters there mentioned have been sufficiently discussed, 

 and the less variable, more important specific distinctions, 

 based upon the character of the venation and shape and 

 position of the sori, may here be treated. 



Venation. — The Calif ornian Nitophylla maybe separated 

 into groups, distinguished from one another by the charac- 

 ter of the venation. In that group which includes the 

 greater number of forms, the species possess a midrib, 

 nerves, and conspicuous veins, developed to a greater or 

 less extent according to the species. Some forms exhibit 

 only the midrib, which passes over at once into the undiffer- 

 entiated frond as in N. under soman uni. Others, again, are 

 provided with a midrib which divides into more or less con- 

 spicuous nerves, the latter passing again into the ordinary 

 frond, e. g., JV. harveyammi and N. ninltilobum. Still 

 other forms, such as N. violaceum and N. riiprechtianiim, 

 show a full development of midrib, nerves, and veins, the 

 last named structures usually conspicuous, and either anasto- 

 mosing or remaining free and flabellate. A second group 

 consists of forms in which no midrib is present, but the sur- 

 face of the frond is marked by a network of reticulate 

 nerves and veins, as in N. latissimicm. The forms of the 

 third group, including N. fryeanuni, N. iincinatiun and N. 

 corallinariini^ are destitute of midrib and nerves, and are 

 provided with scarcely perceptible, usually microscopic 

 veins, which either anastomose with one another, or remain 

 free. A fourth group comprises forms which wholly lack 

 venation of any kind whatsoever, as e. g., N. sfectabile. 



Sori. — The sporangia of Nitophyllum are gathered 

 together into sori of varying shape and size. These latter 

 structures may be employed as reliable specific distinctions 

 in discriminating between species. The Californian plants, 

 taken as a whole, show a considerable range of forms as 

 regards the shape of the sorus, and likewise a considerable 

 variety in its position. Within the limits of certain species, 

 e. g., JV. violaceum and N. riiprechiianimi, these variations 



