SECTION I. 
CHLOROSPERMEA. 
Green Seaweeds. 
Among the most abundant of the common species of seaweeds are two, 
Ulwa latissima and Porphyra laciniata, which form together, when pre- 
pared and potted, the laver of commerce ; the latter, although belonging to 
the chlorosperms, in accordance with its system of fructification, is 
brown, or sometimes a lurid purple. There are several tolerably well- 
defined species of each of these plants, some of which are found abundantly 
on rocky shores, while others are somewhat rare. The species most com- 
monly met with is Ulva latissima (Fig. 5), or the very broad Ulva, or 
Fig. 5. Ula latissima. Fie. 6. Ulwa linza. 
amiliarly, lettuce weed or green laver. This species is found on all shores 
and in ali latitudes, except in the Arctic regions, though even there a small 
stunted species called Ulwa crispa is sometimes met with. The frond of 
Ulva latissima is delicately membranaceous and of a bright green colour ; 
in form it is usually a broad, rounded oblong, from Gin. to 14in. long, often 
very much waved at the margin, and attached to the rocks by a very 
minute disc. The spores are usually arranged in groups of fours, and are 
scattered over the whole frond. 
