THE HALF-TIDE POOL. 53 



we have the example of a stem containing twenty- 

 siphons : the ceramic! ia or seed vessels are seated 

 closely on the stem, and the tetraspores are found 

 on separate plants imbedded in smaller branchlets, 

 which have often thread-like processes at the tips. 

 If examined in the autumn, this plant is sometimes 

 yellowish, and full of oblong yellow bodies called an- 

 the rid ia, a part of its fructification. 



For other Polysiplwnia, see " Low-water Mark." 



KYTIPHLCEA. 



(Name from " wrinkle," and " the bark," in allusion to the appearance 

 of the surface when dry.) 



This is allied to PoIt/sipJwnia, and resembles it m 

 having the same kind of fruit, that is, ceramidia, or 

 urns containing spores ; tetraspores not only in swollen 

 branchlets, but also borne in little leaflets called stich- 

 idia. 



Generic cliaracter. — Frond thread-like or com- 

 pressed, pinnate or divided into smaller branches, 

 striped across, and skin reticulated or like net-work. 



Sttiphloza The/toldes. — This is found in pools, 

 both mid-tide and low water, in tufts from three to 

 six inches high, of dark brownish-purple in the water, 

 drying to an olive tint on paper, to which it does not 

 well adhere. This seaweed grows in shallow pools, 

 and is frequently left dry by the tide. It is extremely 

 like Polysiplionia Nigrescens, but the least morsel seen 

 under the microscope will reveal the difference. In 



