THE MARINE ALGjE OF NEW ENGLAND. 165 



borne in parallel rows. Such collections of tetraspores are called stichidia. The 

 fronds in the present suborder vary greatly. In the more beautiful genera of tropical 

 regions they are in the form of complicated net-works or in membranes in which the 

 cells are arranged in regular order, but in the majority of the genera the fronds are 

 filiform and branching and generally beset, at least at some seasons, with delicate 

 hairs. In most of the genera represented on our coast the fronds have a polysiphonous 

 axis, that is, on cross-section there is seen to be a central cell surrounded by a circle 

 of large cells, and in longitudinal sections there is a central filament composed of large 

 cells, and on each side a lateral filament whose cells correspond in length to those of 

 the central filament, the upper and lower walls of the three cells forming two parallel 

 lines. 



Fronds flattened Odonthalia. 



Fronds filiform , 1 



1. Tetraspores borne in the smaller branches 2 



Tetraspores borne in stichidia 4 



2. Superficial cells small, irregularly placed 3 



Superficial cells, at least in the younger branches, in transverse 



bands Polysiphonia. 



3. Branches filiform throughout Rhodomela. 



Ultimate branches club-shaped, much attenuated at base. Chondriopsis. 



4. Fronds beset with monosiphonous branchlets Dasya. 



Fronds without monosiphonous branchlets, superficial cells quad- 

 rate Bostrychia. 



OHONDEIOPSIS, J. Ag. 



(From xovdpoc, cartilage, and oi[)ic, an appearance.) 



Fronds brownish red, terete or subcompressed, pinnately decompound, 

 branches virgate, much constricted at the base, composed of a monosi- 

 phonous axis surrounded by a few (4-6) siphons and surrounded by sec- 

 ondary siphons, cortex of small polygonal cells; antheridia borne in 

 short disk-like branchlets covering both surfaces except at the margin j 

 tetraspores tripartite, in club-shaped branchlets ; cystocarps sessile, 

 ovate, with a distinct carpostome, spores pyriform, on short pedicels 

 from a basal placenta. 



A genus of which about twenty species have been described, which inhabit princi- 

 pally the warmer parts of the world, some being widely diffused. They are as a whole 

 difficult to distinguish, the specific marks being principally the ramification and shape 

 of the branchlets, points in which the different species vary very much. The anther- 

 idia are very peculiar. On the upper branches are borne flattened, more or less in- 

 curved, disk-sbaped branches, whose margin is wavy. The antheridia cover both 

 sides of these discoidal branches, except at the margin, which is composed of large 

 hyaline cells. The fronds are intermediate between those of Rhodomela and Laurencia, 

 and tbe branchlets are always much constricted at the-base. Most of the species were 

 formerly included by Lamouroux and others in the genus Laurencia. By C. A. Agardh 

 they were, in the Species Algarum, placed in Chondria, a genus retained by Harvey in the 

 Nereis. Since as originally defined the genus Chondria embraced algse of rather remote 

 relationship to one another, J. G. Agardh, in the third volume of his Species Algarum, 

 separated the present group, under the name of Chondriopm, the name Chondria being 



