(154) 



broad, in the younger about as long as broad. The structiu'e internally 

 is composed of minute quadrate cellules, externally the surface is slightly 

 striated. Fronds two to five inches long, rigid, scarcely adhering to the 

 paper in drying. Colour, dark olive green. 



A most variable species, exhibiting in its summer, autumn, and winter 

 states as great a diversity of ramification as is to be found almost in 

 any other Algse ; so great, that more than one species has been contended 

 for by some of the Continental botanists, but Dr. Harvey has come to a 

 different, and, w^e think, a more accurate conclusion. In sea-weeds, 

 more than in the land plants, is careful, patient, and continued obser- 

 vation necessary, in order to arrive at anything like a just idea of the 

 limits of species : so variable are the influences to which they are 

 exposed, from the ever-changing medium in which they grow, that 

 nothing but a most rigid and careful study of specimens, collected under 

 every possible circumstance, and over a wide area, can justify us in 

 deciding the claims to specific distinction in the case of such poly- 

 morphous species. 



The present species is by no means of uncommon occurrence in the 

 south, but seems to become scarce as we proceed northwards. 



It is a larger, much harsher, and more bushy plant than the preceding, 

 with the pinnules more spine-like, and may be readily known by the 

 different structure of the stem. 



EXPLANATION OF PLATE CLXXIL 



Fig. 1. — Sphacelaria scoparia, natural size. 

 2. — Pinna. 



3. — Portion of young stem. 

 4. — Portion of old stem. 

 5. — Portion of young stem. All magnified. 



