DASYCLADEiE. 35 



SYNOPSIS OF THE NORTH AMERICAN GENERA. 



I. Cymopolia. Frond with a calcareous, branching, articulated shell ; the internodes 



honeycombed ; apices emitting pencilled ramelli. 



II. Dasycladus. Frond soft, unbranched, set throughout with closely placed whorls of 



trichotomous, horizontal ramelli. 



III. Acetabularia. Frond with a filiform, incrusted stipes, terminating in a peltate 



disc formed of radiating fruit-cells (sporangia.) 



I. CYMOPOLIA. Lamour. 



Frond filiform, dichotomous ; its outer crust (or shell) calcareous, thick, distinctly 

 articulate, the articulations everywhere pierced with pores, and the younger nodes 

 frino-ed with byssoid, multifid fibrill*. Inner frond (enclosed in the crustaceous shell) 

 a membranous, continuous branching hollow tube, nodoso-constricted and moniliform, 

 but not septate ; the nodes when young fibriUiferous, at length bare ; the inter-nodes 

 whorled with several rows of short, horizontal, 3-4-fid, club-shaped ramelli, winch pro- 

 trude through the pores of the outer crust. Sporangia globose, borne on the club- 

 shaped ramelli. 



The frond in this genus consists of two distinct and separately organised systems- 

 one mineral, and which wholly disappears when the plant is put into muriatic acid ; 

 tlie other vegetable, of the same texture, substance, and very similar organization to 

 the frond of the following genus (Dasycladus); but still more nearly akin to another 

 genus Neomeris, not yet recorded from our shores, but which very probably exists on 

 the Florida reefs, as one of its species is found in the West Indies. For sake of greater 

 clearness, I have, in the above diagnosis, first described the outer crust, or frond, as it 

 appears when lifted from the sea ; and then given the characteristics of the vegetable 

 axis which is brought to light when tlie calcareous envelope has been removed by acid. 

 When the plant is alive, and seen under water, its green colour, and the rich pencils of 

 delicate, bright green byssoid fibres that crown all the growing branches and their 

 division's, at once suggest its vegetable nature. But when seen dry and dead on the 

 shore, where all these fibres and the green colour disappear, the resemblance to a po- 

 rous zoophyte is so great, that it is no wonder that this Alga shoidd, until quite recently, 

 have had a place in the animal kingdom. The pores of the crust may easily pass for 

 polype cells, and the enclosed tube has, when dry, an almost horny consistence. 



