204 



SCIENCE-GOSSIP. 



[Sept. 1, 1865. 



SEA-WUACK. 



Ever drifting, drifting, drifting. 



On the shifting 

 Currents of tlie restless main ; 

 Till in sheltered coves, and reaches 



Of sandy beaches, 

 All have found repose agam. 



Lijiigfellow'' s " Sea-wccd." 



OF all the objects ■which the ocean casts upon its 

 shores for the amusement of visitors from 

 town, none are better known than the heaps of 

 coarse black sea-weed which some call "wrack," 

 and some call " tang," and some know not what to 

 call. Sea-weeds are classed in three groups — the 

 red, the green, and the olive. The species under 

 notice belongs to the last of these. When found 

 lying upon the beach it certainly looks as much like 

 black as a lump of charcoal, but when growing in 

 the sea is as decidedly olive. But we are speak- 

 ing of it as though there were but one species, 

 whereas two, three, or four, are often mingled in 

 the same heap, and our object is to point out the 

 diiferences, and furnish names whereby they may be 

 distinguished. 



Eirst, there is the Black Tang, or Bladder-wrack 

 {Fucks vesiculosns), with long fronds sometimes two 



the fronds will sometimes be noticed swollen, and 

 covered with little tubercles, scarcely raised above 

 the surface. These contain the fructification. Let 

 us pause a moment to examine them more minutely. 

 We shall observe that each of these little frustules has 

 a minute opening through which their contents es- 

 cape. Cut one of these tips across, and each frustule 

 will be seen to represent a cell or internal cavity 

 (flg. 2, a), enclosing, in one plant, what are called the 

 cmthendia, and in another the spores. The former 

 of these we may regard as the male, and the latter 

 as the female organs. Both are always produced on 

 separate plants. The antheridia are little bags or 

 vesicles, containing small bodies called zoospores {b), 

 which no sooner escape than they move about in the 

 water as if endowed with life, and conduct them- 

 selves like little animals. The spores are little 

 grains, of an oblong shape, which ultimately 

 separate into a definite number of parts {c) ; these 

 perform the functions of seeds, which are fertilized 

 by the zoospores, as the ovules are fertilized by the 

 pollen of flowering plants. We cannot, within our 

 present limits, enter upon the mysteries of increase 

 and multiplication in sea-weeds, but must content 

 ourselves with indicating what any good book on 

 the subject will more fully explain. 

 The Serrated Wrack {Fucus serratus) resembles 



! . Black Tang, or Bladder-wrack 

 (Funis vesiculosua). 



or three feet in length, forking again and agai'n into 

 what we may call branches, with a stout midrib 

 running down the centre, and covered with warty 

 tubercles, or bladders, arranged in pairs (fig. 1). 

 These arc hollow, and filled with air, so as to render 

 the "wrack" buoyant in the water. The tips of 



Fig. 2. Serrated Wrack {Funis serratus). 



the last in form, but there are no air-bladders, and 

 the edges of the fronds arc jagged or serrated, like 

 the tooth of a saw (fig. 2). Injike manner the fruit 



