SEA WEEDS 383 



scattered over the surface of the frond as so many black dots, and 

 the antheridia are elongated, cylindrical bodies attached to tufted 

 filaments on all parts of the frond. 



In the genus Stilophora the root is discoid ; the frond cylin- 

 drical, hollow, and branched ; and the spores arranged in clusters 

 over the surface. One species (8. rnizodes) is occasionally to be 

 seen on the south coast. It is of a yellowish colour, from six 

 to twenty inches long, and may be known by its long thread-Eke 

 branches, with scattered, forked branchlets, and by the wart-like 

 projections of the stem which contain the spores. This weed is 

 often the source of some disappointment to the collector, for it soon 

 turns to a jelly-like mass when removed from the water, and should 

 therefore be mounted as soon as possible after it has been collected. 



The fennel -like DictyosipTion foeniculaceus is abundant in tide 

 pools, where it may be seen in its best condition during spring 

 and early summer. Its root is a small disc, the frond is tubular, 

 thread-like and branched, and the branches bear hooked branchlets. 

 The spores are naked, and distributed either singly or in clusters 

 over the surface of the frond. 



Our next genus Punctaria contains a few British species with 

 a shield-shaped root, and a flat, membranous, undivided frond, 

 without a midrib, and having the spores disposed as minute dots 

 over the surface. A plantain-like species (P. plantaginea) has 

 broad, leathery, lanceolate fronds, of a dark olive-brown colour, 

 usually from six inches to a foot in length. Two other weeds the 

 broad-leaved P. latifolla of the tide pools, and the slender, tufted 

 P. tenuissima, which is parasitic on Zostera and some algse, are 

 sometimes regarded as mere varieties of P. plantaginea. 



In the genus Asperococcus the root is shield- shaped, and the 

 frond is a membranous tubular sac of two distinct layers. The 

 colour is pale green, and the general appearance very similar to 

 that of Ulva. The spores are arranged in small oblong clusters 

 which appear as dark dots on the surface of the frond. A. compressus 

 has slightly swollen flat fronds of a linear lanceolate form, taper- 

 ing below. It grows in deep water, but is often washed up during 

 storms. A second species A. Turneri has large, puffy, green 

 fronds, contracted at intervals, and grows in tufts on rocks between 

 the tide-marks, being specially partial to muddy shores. The 

 genus also includes the prickly A. echinatus, the long, thin fronds 

 of which grow in dense tufts in deep water. 



The last genus of the order is Litosiphon, a parasitic group 



