386 



THE SEA SHORE 



FIG. 272. Desmarestia 

 ligulata 



dried and mounted as quickly as possible. D. Ugulata, so named 

 from the flat, strap-like frond, is common on all our coasts. It is 

 pinnately branched, and all the branches andbranchlets taper towards 

 both ends. D. viridis has a cylindrical, 

 thread-like, and freely-divided frond, with 

 opposite branches and branchlets. It 

 occurs more commonly on the northern 

 shores. 



The last order of olive-spored weeds 

 is the FucacecB, some species of which 

 are so abundant between the tide-marks, 

 from high-water to low-water levels, that 

 they form a verji important charac- 

 teristic of our shores. They are mostly 

 large, tough, and leathery weeds, without 

 joints, and the spores are contained in 

 spherical receptacles embedded in the 

 substance of the frond. 



In the typical genus Fucus the root 

 is a conical disc, and the frond flat or com- 

 pressed and forked. Most of the species are furnished with one-celled 

 air-vessels in the substance of the frond, and these serve to buoy up 

 the plants and keep them more or less erect when submerged. The 

 spore-receptacles are usually embedded near the tips of the branches, 

 but are sometimes borne on special branches or shoots. They are 

 filled with a slimy mucus and contain a network of jointed fila- 

 ments. The weeds are very hardy, capable of withstanding long 

 exposures to air and sun, and are sometimes to be found above 

 high-water mark, where they are watered only by the spray of the 

 waves for a brief period at intervals of about twelve hours. Al- 

 though they are not usually looked upon as ornaments in the 

 collector's herbarium, they will repay examination for the tufts of 

 smaller and more beautiful weeds to which they often give attach- 

 ment and shelter. 



Four species are common on our coasts, and these may be 

 readily distinguished by the most cursory examination. The Ser- 

 rated Wrack (F. serratus) has a flat, forked frond with toothed 

 edges and a strong midrib, ranging from one to four feet long, and 

 no air-vessels. The Knotted Wrack (F. nodosus Plate VII.) may 

 be known by its flattened, thick and narrow frond, without a distinct 

 rib, from one to five feet long. The branches are narrow at the 



