V. SPrLEROCOCCOIDE.E. 103 



a pulvinate tuft of simple or dichotomous spore-threads whose terminal cells are 

 earliest ripened : spores elliptical or roundish. TeiraRj)ores tripartite, grouped in 

 definite spots or sori, variously dispersed over the frond. 



This genus is nearly related to Delesseria, from which it is only to be distinguished 

 by its unsymmetrical frond destitute of a single percurrent midrib. This character 

 will generally be found sufficient readily to distinguish these groups, but some 

 species of the southern hemisphere exhibit intermediate stages ; as Delesseria dicho- 

 toma and Nitophylliim multinerve which sometimes approach each other inconveniently 

 near. 



A considerable number of species have been described, which Kiitzing divides 

 into three genera, Aglaiophyllum, Schizoglosstwi, and Cryptoi'ileura, distinguished by 

 some differences in the structure of the frond. Aglaiophyllum is limited to those 

 species Avhich are altogether nerveless, and have a membrane composed of a single 

 stratum of large cellules: Cryptopleura to those in which nerves are more or less 

 obvious, with a similarly constructed membrane : and Schizoglossum to such nerve- 

 less species as have a membrane composed of more than one stratum of cellules. 

 I do not adopt these genera, because I find the characters untenable. The more or 

 less nervated frond varies even in the same species ; Scldzoglosswu GmeUni,Kutz. for 

 instance, which ought, by generic character, to be nerveless, is frequently abun- 

 dantly supplied with nerves, much more abundantly than Cryptopleura Bonnemai- 

 soni and C. Crozieri. The character founded on compound structure is equally 

 nugatory, for Cryptopleura lacerata, which is, moreover, the type of tlie genus so 

 called, has a frond constructed of more than one row of cellules, contrary to the 

 generic character. There is, indeed, a most close affinity in structure between S. 

 Gvielini and C. lacerata, and they cannot be separated genorically without violence. 



With respect to nomenclature, I prefer retaining the name Nifophylltnn, under 

 which this genus was first defined, although it may not be constructed on classical 

 principles, to adopting the modern, more classical, but less euphonious, and as I 

 think unnecessary Aglaiophyllum of my friend Dr. Montague. The change of long 

 established names, except in cases of clear necessity, is very objectionable ; and if 

 all names in natural history were to be rejected that are not founded according to 

 strictly classical rules, a large number of new synonyms would soon be added to the 

 copious list already a burden to the science. 



One of the more distincti\'e features of the marine flora of the Atlantic coast of 

 America as compared with that of Europe is, as has been already noticed in our in- 

 troduction (Part i, p. 24), then early total absence of species of Nitophyllum, a genus 

 which abounds on the European coasts, where many kinds are dispersed from the 

 shores of Scotland to those of Spain, and in some places in such profusion tliat they 

 give the chief character to the vegetation, at certain depths. In contrast to this I 

 can only as yet claim, for the North American seaboard, a few scraps, almost too 

 imperfect for determination. Very different is the case on the shores of South 

 America, beyond the tropic, where the genus flourishes in many fine species, as also 



