134 HELMINTHOCLADEiE. v. 



which are three or four times compounded, the divisions irreguhxrly alternate, and 

 spreading at right angles. The ramuli scattered, cylindrical and obtuse. Pmpheric 

 filaments irregularly branched, moniliform. Nuclei abundant. 



Possibly this may be distinct from the European plant. The axial and peripheric 

 filaments are rather more robust than in British specimens with which I have com- 

 pared Dr. Blodgett's, but in other respects, internal and external, the two plants 

 nearly coincide. The structure of the nuclei offers nothing peculiar. 



1. NEMALION. Duly. 



Frond cylindrical, gelatinous, elastic, dichotomous, with a cord-like axis clothed 

 with a continuous periphery of filaments invested in gelatine ; the axis composed 

 of elongate, simple, longitudinal, interlaced filaments forming a medullary column, 

 and surrounded by anastomosing threads fi'om which issue the horizontal, dichoto- 

 mous, fastigiate, moniliform filaments of the periphei^y. Sporiferous-nuclei immersed 

 among the filaments of tlie periphery, spherical, composed of numerous clavate 

 spore-threads radiating from a central point. Tetraspores " formed in the terminal 

 cells of the peripheric filaments, triangularly divided, with prominent sporules." (J. 



The fronds are worm-like, either nearly simple or dichotomously branched, of a 

 dull purple colour, and a highly elastic, gelatino-cartilaginous substance, shrinking 

 very much in drying. A cross-section shows a very densely compacted medullary 

 cord or axis composed of interwoven, twisted, slender, longitudinal filaments, 

 giving off obliquely to all sides horizontal, dichotomously-divided branches which 

 form the periphery. The evolution of the frond is thus described by Prof J. 

 Agardh : — " The different strata of the frond seem to me to be formed in an oppo- 

 site direction. First, unless I am deceived, the peripheric stratum begins to be 

 developed, from the base upward, by progressive evolution ; some of the branches 

 emitted by the peripheric filaments constitute the peripheric stratum, but others 

 are erected, with a direction more vertical, giving off on their outer side new peri- 

 pheric filaments, and on their inward side longitudinal filaments. These latter, at 

 first, by an oblique course are directed towards the centre of the axis ; then they 

 take a downward direction, by a longitudinal course. In some respects, therefore, 

 the mode of growth of the Endogenous stem is imitated. The filaments proceeding 

 downwards are inarticulate and cylindrical ; those growing upwards are articulated, 

 and more or less contracted at the dissepiments. So that one may describe the 

 stratification as threefold ; a medullary stratuni formed of longitudinal, simple fila- 

 ments, an intermediate of obliquely horizontal, anastomosing filaments and a peri- 

 pheric of horizontal, dichotomous, fastigiate filaments." 



