BOT.-VOL. II.] NOTT~CALIFORNIAN NITOPHYLLA. II 



may be either simple and unbranched, as is commonly the 

 case in N. multilobum, or it may become considerably 

 divided, as in N, rttp'cchtianum. Frequently it does not 

 extend in the frond beyond the upper portion of the stalk 

 or lower segments. In other cases its ramifications reach 

 out into the branches almost to their tip, and there evan- 

 esce, or divide into nerves. 



Nerves. These structures are a characteristic feature of 



the frond in several species, reaching a high degree of 

 development in some forms. In N. latissimum no midrib is 

 present, but the large membranous frond is supported by 

 a network of intersecting nerves and veins of considerable 

 prominence. The other species are not distinguished by 

 such a full development of these structures. Usually the 

 nerves are limited to the outer margins or apices of the 

 frond, where they become flabellate or anastomose freely 

 with each other. 



Veins. More or less conspicuous veins constitute a note- 

 worthy structural element in some species, especially in iV: 

 rufrechiianimi and N. violaceimi. In these plants, particu- 

 larly where the frond is at all flabellate, a rich development 

 of the finer venation may be seen, whose ramifications 

 extend in a flabellate fashion throughout the frond, or, in 

 some cases, anastomose with one another, finally becoming 



free. 



In N.fryeanum, N. uncinatum, and N. corallinartmi the 

 midrib and conspicuous veins are entirely wanting and the 

 only trace of venation is .seen in the microscopic veins 

 which characterize these species. These minute structures 

 are frequently very delicate and invisible to the naked eye. 

 They extend as a rule throughout the frond, branching 

 freely or anastomosing. In N.fryeanum, however, the del- 

 icate veins, in nearly every case, become somewhat stouter 

 toward the base of the erect frond, where they form a more 

 or less conspicuous fan-shaped area. A single species, N. 

 sfectabile, is destitute of any sort of veins. 



Variable and Fixed Characters.— \\ has been said in a 

 preceding portion of this paper that stress should be laid 



