DASYCLADE^. 33 



their lower half, and beset with ramuli only above. The ramuli are exceedingly slen- 

 der, many times more so than the part of the branch from which they spring, and are 

 generally furnished with opposite or scattered, slender pinnules. The colour is a pale 

 yellow green ; the substance exceedingly soft and tender. 



The figure given in Phyc. Brit., taken from West of Ireland specimens, does not 

 very well represent the Key West plant, which, however, closely resembles specimens 

 from the South Coast of England and coast of Normandy, except that they are rather 

 more luxuriant. This plant is generally of a much paler colour and still softer sub- 

 stance than B. plumosa, and is distinguished from the varieties of that plant by its 

 ramuli being compound (pinnate), as well as greatly more slender than those of 

 B. plumosa. 



Order II.— DASYCLADE^. 



DasycladecB and Polyphysece, Kiitz. Phyc. Gen. p. 311-312. Valoniece, in part. 

 Kiitz. Sp. Alg. p. 507- Part of Siphonece, Auct. alior. 



Diagnosis. Green, marine Alg^e, naked, or coated with carbonate of lime, having 

 a unicellular simple or branched axis, which is whorled, either throughout its whole 

 length, or near the summit, with articulated ramelli. Spores spherical, developed in 

 proper fruit-cells. 



Natural Character. Root formed of tubular, elongated, branching fibres more or 

 less matted together. Frond either simple or branched, essentially consisting of an axis 

 and of ramelli. The axis is in all cases a continuous tube, without articulation or sep- 

 tum, running throughout the frond, containing endochrome in a young stage, but very 

 frequently found empty in the mature plant ; and is apparently formed by the evolution 

 of a single cell. Its walls are thick, tough, and readily seen, when a cross section is 

 examined under the microscope, to be composed of successive concentric layers of cellu- 

 lose. At regular intervals, either throughout the whole length of the axis, or in its 

 upper half only, the tube is pierced by a circle of holes, and from these holes there issue 

 whorled, articulated, confervoid ramelli, which appear to discharge the functions of leaves, 

 and are sometimes deciduous, sometimes persistent. In the less complex genera, Poly- 

 physa and Acetabularia, the ramelli are extremely delicate and fugacious, and are found 

 only on young plants, or during the process of evolution ; their position being indi- 

 cated on plants from which they have fallen, by the circle of holes in which they had 

 been inserted. In Dasycladus the ramelli are permanent, and thickly clothe every 

 part of the stem, in whorls sometimes very closely placed, sometimes sub-distant ; but 

 there is no connection among the ramelli or between the whorls. In Neomeris the 

 structure of the stem and ramelli is very similar to that of Dasycladus^ with this dif- 

 ference, that the apices of the ramelli cohere to form an investing membrane or epidermis 



F 



