GEOGRAPHICAL DISTRIBUTION OF ULV^E. 91 



this is the case in winter and early spring, when the 

 plant is collected for table. Later in the year the 

 fronds are of stunted size and more or less olivaceous 

 colour, and much less suitable for gathering. The plant 

 appears to be of very rapid growth and decay, a few 

 weeks sufficing for its full development. Like many 

 fugitive plants, however, it is not confined to one 

 season, but continues to develope throughout the 

 year; but with this difference, that the plants deve- 

 loped in summer are very much smaller, more tena- 

 cious, and of a dull colour. These last are regarded 

 by some authors as a different species, and called 

 P. unibilicata. 



There is a circumstance connected with the history of 

 our common Ulvce, Enter omorphce, tmdPorphyrce, which 

 deserves notice. Most of the species common to the 

 European shores are found in all parts of the world to 

 which a marine vegetation extends. In the cold waters 

 of the Arctic Sea, Ulva latissima, Enteromorpha com- 

 pressa, and Porphyra laciniata, vegetate in abundance ; 

 and these same plants skirt the shires of tropical seas, 

 and extend into the southern ocean as far as Cape Horn. 

 Vegetation, at least with its most obvious features, 

 ceases in the south at a much lower parallel than in the 

 Arctic regions, and the shores of the Antarctic lands 

 appear to be perfectly barren, producing not even an 

 Ulva. But the fact of the great adaptability of plants of 

 this family to different climates, is beautifully illustrated 

 by the last land-plant collected by the acute naturalist 

 attached to our Antarctic expedition. The last plant 

 that struggles with perpetual winter was gathered at 



