Ch. X] 



THE BROWN ALG.E 



441 



forms occur in high northern seas, probably because cold 

 waters dissolve more gases than warm. On the Pacific 

 coast occurs Nereocystis, with its very long 

 stalk, single great float, and several broad 

 blades, while Postelsia, the Sea Palm, has a 

 stiff stem, a foot high, with a crown of 

 fronds (Fig. 307). The great Macrocystis 

 of South Pacific waters has a float at the 

 base of each blade of the frond (Fig. 133), 

 and becomes 200 or more feet in length. 

 They all reproduce by the conjugation of 

 small ciliate gametes (long mistaken for zoo- 

 spores and thus recorded in most books), 

 which are formed in special cells developed 

 in irregular patches on the surfaces of the 

 fronds; and the resulting zygospores grow 

 directly to new plants like the parents. 



While the 

 great Kelps 



are the 

 principal 

 members of 

 this order, 

 there also 

 occur some 

 small and slender forms which, fig7306.— Lam- 



except for their Color, Suggest inaria saccharina; 



Confervales. In one of these, x *' he upper ^ 

 Ectocarpus, common in clear run- ment can be seen 

 ning waters, the gametes are $?%£%S&£ 

 formed in a multicellular struc- duce the gametes, 

 ture. This is the first instance (From 01toanM -> 

 >08teisia thereof m the ascending scale, and another 

 palm a for- anticipation of conditions prevailing in the 

 (From Pot hig ner plants. " Anticipation " of course has 

 tfiism.) nothing to do with morphological oiigin, 



Fig. 



