10 SYNOPSIS OF SEAWEED TRIBES. 



GENERA OF THE FUCUS TRIBE. 



Haxidrys — Air vessels, long, pod-shaped. 



Cystoseiea — Air vessels in the branches; receptacles small. 



Pycnophyctjs — Root composed of branching fibres; recep- 

 tacles cellular. 



Eucus — Root a round or flattened disc; receptacles large, 

 filled with mucus, traversed by jointed threads. 



Himanthalia — Erond round, small, and cup-shaped; recep- 

 tacles resembling fronds, very long, repeatedly forked. 



GENERA OE THE SPOROCHNUS TRIBE 



FAMILY I., OF THE ARTHROCLADIA, 



With their spores attached to slender filaments. 



Desmaeestia — Erond solid, either filiform or flat, distich- 

 . ously branched. 



Arthrocladia — Erond cylindrical, furnished with whorls of 

 small slender jointed filaments. 



FAMILY II., OF THE SPOROCHNTJS, 



With their spores produced in knob-like receptacles. 

 Sporochnes — Receptacles lateral, on short stalks. 

 Carpoiiitra — Receptacles terminal at the tips of the brandies. 



GENERA OE THE LAMINARIA TRIBE. 

 Alaeia — Leaf with a distinct mid-rib. 

 Laminaeia — Erond without a mid-rib. 

 Chorda — Erond cylindrical, unbranched, hollow, and con- 

 stricted at intervals. 



GENERA OE THE DICTYOTA TRIBE. 



Ctjtleria — Erond ribless, irregularly cleft ; sori dot-like, and 

 scattered. 



