66 BRITISH MARINE ALG. 
covering both surfaces of the fronds. Dr. Harvey mentions a variety of 
this species, called vermicularis, found by Mrs. Griffiths, in Torbay, the 
fronds of which are very narrow, and filiform or stringlike, and more or 
less twisted or curled. This variety is still abundant in various parts of 
Torbay, its habitat being in shallow rock pools about half-tide level. 
Young plants of this variety are sometimes very similar to undeveloped 
specimens of Chorda lomentaria (Fig. 44): the latter are, however, much 
smoother to the touch, and the colour is always a more decided greenish 
olive. 
The Chordariacee are a group of plants which are usnally characterised 
by botanists as olive-coloured sea-weeds, the fronds of which are, in 
some, of a gelatinous nature, while in others, the whole substance. of the 
plants is cartilaginous, made up, as it were, of a crisp gristle-like body, 
which spreads over rocks and stones and adheres to them by its under sur- 
face. Some of these, as, for instance, Leathesia tuberiformis (Fig. 72), 
are sometimes found about half-tide level, covering the rocks in exten- 
sive masses of a light olive or yellow colour, heaped together like 
variously shaped tubers, and the same species is found frequently 
growing in small roundish groups on other seaweeds. Some others 
of this order are parasitic, composed of densely-tufted filaments, for 
the most part minute, some being entirely microscopic, the structure 
and fructification of which, when viewed under a high power, are 
wonderfully beautiful. Few of this order of plants are particularly 
attractive to the general collector, and many of them are extremely diffi- 
cult to prepare for the herbarium. I shall, however, give a few direc- 
tions as to the proper method of drying and pressing these plants as I 
severally describe them. 
Some of the Chordariacee are very widely dispersed, a few of our 
common species, such as Leathesia and Chordaria, being found as abun- 
dantly on the South African shores and elsewhere, as on those of this 
country. In describing the British species of this order, I purpose grouping 
them. together on the same principle which I observed in describing the 
three divisions in the Dictyotacee. Thus, the two first genera contain 
plants which have cylindrical branching fronds; the two next consist of 
tuber-shaped fleshy or cartilaginous masses; and the two last are dense 
tufts of unbranched thread-like filaments, in almost every instance parasitic 
on some particular species of seaweed. 
The genus Chordaria is so named from the plants which are included in 
it having exactly the appearance of dark-coloured strings or bundles of 
twine. Fig. 70 represents the well-known species Chordaria flagelliformis 
the scourge or whip-like Chordaria. This plant is a summer annual, and 
grows in rock pools between tide marks. The fronds are from a few inches 
to 2ft. or 3ft. long, having a central stem for about half the length of the 
plant, the upper part being irregularly divided or branched, the lower 
portion bearing here and there on each side, short ramuli, mostly of the 
same thickness and consistency as the stem and branches of the plant. In 
