202 



KNOWLEDGE & SCIENTIFIC NEWS. 



[August, 1905. 



Sea. weeds : 



A HolidaLV Pamper for Field 

 Bota.nists. 



By David W. Hevax, Scarboroug^h F.\. ScK'iety. 



Most botanists will, during their summer holidays, stick 

 to the cliff and sand dune to seek maritime, not marine, 

 plants. But it seems a pity that the latter should receive 

 such scant attention. The beauty of many of the sea 

 weeds is so exquisite, the way of life of others so inter- 

 esting, that the field botanist cannot afford to miss 

 them, and this is specially the case if he possesses a 

 microscope. .\ shore that possesses a rocky reef, laid 

 bare twice daily by the ebbing tide, is the best collecting 

 ground, and as this article is penned at Scarborough it 

 may not be out of place to mention that it is an ideal 

 place in this respect. Arrived on the scene with a tin 

 canister or two — a bottle of sea-water is also needed, but 

 should not be carried on the slippery rocks — we proceed 

 to take " snippings" of everything we come across. 



It is noticed at the outset that the seaweeds tend to 

 be clannish. Tlie green ones favour, on the whole, the 

 part towards high-tide mark, and the brown the part 

 between tide mark.s. .\ good many red flourish there, 

 too, but as a rule their red is a very poor red — nearlv 

 black or faded yellow. It is mostly in the deepest pools, 

 and out in those deeper reaches that are never laid bare 

 by the tide that those splendid crimsons and rosy reds 

 occur that arc the typical colours of the red seaweeds. 

 To get these last we must wait till a storm tears them 

 from their moorings and casts them on the shore. 



ITie brown seaweeds are the giants of the shore, and 

 claim our attention very much, for they are slippery 

 cu.stomers. Growing on the margins of all the pools 

 are the Wracks {Fuciis), all of which branch, by re- 

 peated division into two (dichotomy), much like the 

 flowering stalk of the Stitchwort, but always in the 

 same plane, so that if we spread a plant out on the 

 sand it forms a perfectly flat, fan-shaped frond. 1 ho 

 Bladder Wrack (F. vesiculosus) has paired bladders 

 in the frond (Fig. i). The Serrated Wrack {F. serratus) 



Pig. I. 



Fisr. 2. 



is without bladders, and has, as its name indicates, a 

 saw-like edge to the frond (Fig. 2). The Knotted Wrack 

 (F. nodosus) is "all stalk," with big bladders in the 

 stalk like a string of oval In-ads. and its frond has no 

 flat, leafy expansion or blade. It does not divide 

 dichotomously, and in other respects, stated further on 

 it differs from the typical Fucus (Fig. 3). This olant 

 seems particularly happy in tidal river mouths where 



the water is only slightly salt. F. canaliculatiis has 

 channelled Ironds, and grows only three to six inches high. 

 Then there is the fine, bushy Sea Oak {Ha/idrys 

 siliqiwsa) in great plenty in the deeper pools, known by 

 its pod-like bladders, which are seen, on being split by 

 a penknife, to contain several storeys (Fig. 4). Lastly, 



not to stay among the Wracks too long, there is the 

 delightful .Sea-thong (Himanthalia lorea), growing at 

 dead low-tide mark. There they grow in scores — well 

 worth a snap-shot — like little brown mushrooms when 

 young, but in their second year they put out a long 

 strap-shaped dichotomous frond from two to three feet 

 long, which is the reproductive part (Fig. 5). 



Here at low water we see the Tangles (Laminaria 

 digilata), a stout st.ilk which may reach three feet 



long or more, bearing a broad fiat ma.ss of ribbons on 

 the top. This upper frond is shed in spring and a nev/' 

 one grow.s there and splits into ribbons in due course. 

 One sometimes finds both old and new fronds on the 

 one stalk (Fig. 6). 



The most interesting thing .ibout the l-'ucoids is their 

 reproductive arrangeinents. Everyone has noticed the 

 swollen ends of the fronds of the Wracks beset with 



