DKSCUII'TrON OF THE SIMX'IKS. 1(M 



In tlie ItniiK'liiiig- of tlie racliis wo have the fern ratlier than cycadean 

 character, although Boirenia shows that this is not necessarily solely a 

 fern featnre. We can hardly assume that Boiceiiia is the only branching 

 cycad that ever existed. It is more natural to suppose that it is a survivor 

 of a group of branching cycads that once possessed numerous forms. 

 The nervation of the lower jjortions of the pinnules is rather tliat of ferns 

 than of cycads, but Stangeria shows that similar nerves may exist in 

 cycads. The very long, slender, deeply forking nerves in the summits of 

 the pihnules are similar to those of c)^cads. The peculiar spiny teeth are 

 decidedly like those of cycads, but the teeth pas5 below on the frond into 

 lobes, and these lower down graduate into segments that we may call 

 pinnides, and this feature is clearly fern-like. The nerves are immersed 

 in the dense leaf-substance, so that they are often obscured. 



The singular plant Zamiopsis Jac'miata, given on Fl. LXVI, has so 

 many features that cause it to differ from the typical forms of Zamiopsis, 

 that it may well be questioned whether or not it should be made a new 

 ■ genus; but as it has some features allying it to the typical Zamiopsis, I 

 l^lace it with a good deal of hesitation in that genus. So long as no 

 fructification is found with these plants their true position can not be 

 positively deterinined; meantime they may be placed provisionally among 

 the ferns. This type forms (juite an important element in the Potomac 

 flora. 



Zamiopsis pinnatifida, sp. nov. 



Plato LXI, Fig. 7 ;' Pl.ato LXII, Fig. r>; Pl.ato I.XIV, Fig. 2; Plato LXVII, Fig. 2. 



Frond large, arborescent ? ; principal rachis keeled on the under side, 

 strongly ridged on tlie upper margins, probably tripinnate ; pinnules or 

 reduced piniuv alternate, attached by the middle of the narrowed base, 

 oblong, terminated by usually two acute shallow teeth in tlie basal por- 

 tions, cut down nearly to the midrib into ovate denticulate lobes or pin- 

 nules; u[) higher on the pinnules or reduced pinmc these pass into ovate 

 teeth, which become more and more shallow. On the basal lobes or 

 pinnixlcs there are on each margin two or three shallow spinous teeth ; 

 midnerve of the ultimate pinn;\3 or pinnules strong at base, rapidly atten- 



MON XV 11 



