204 ALG. [CHAP, 
forks; the blade being pressed in while the stem is 
fresh and soft, is securely fixed by contraction of the 
latter in drying. But probably the most remarkable 
genus of these dark-spored Alg@ is Macrocystis. 
“From a much-branched root springs, in the first 
instance, a small forked frond which alone bears the 
fruit in clouded patches. .. . Besides this, however, 
arise one or more tall, slender stems, several feet in 
length, with a vertical, terminal, lanceolate frond, 
which is repeatedly split from the base upwards in 
such a way as to form new leaves, the attenuated 
base of which gradually passes into a short petiole, 
which becomes inflated above into a bladder. The 
original frond is thus repeatedly divided in a secund 
manner, till the plant becomes hundreds of feet long. 
As, however, the stem does not increase in strength 
as the plant elongates, the strain is at length so 
great, notwithstanding the numerous bladders, that 
it at last gives way, and the plant floats. Many 
species have been proposed by authors, but all are 
reducible to one, JZ. pyrifera, which girds the’southern 
temperate zone, and stretches up from thence along 
the Pacific to the Arctic regions, through 120 degrees 
of latitude. This plant, like the Sargassum, has 
been celebrated by all voyagers, to whom it is of 
creat value in indicating the presence of rocks, acting, 
as it does, like a great buoy. Vast masses are thrown 
up on exposed coasts, where it is rolled by the waves 
till it forms cables as thick as a man’s body. Single 
plants have been estimated on reasonable grounds as 
attaining a length of 700 feet.”—Berkeley. 
Mr. Darwin, in his “ Voyage of the Beagle,” gives 
