210 
THE SEAWEEDS 
The genus may be divided into three groups. 
A. — Alternating series of three or more pinnellae. Cystocarps sessile 
on the margins of the famuli, solitary. 
1. Sporophylls marginal, branched. Laciniae entire. 
Rami-slender, 1 mm. diameter P. leptophyllum 
Kiitzing. 
South Australia (Investigator Strait, Eastern Bays). 
Fig. 74. — Plocamium leptophyllum: a and h, plants (i>, 
enlarged); c, cystocarps; d, tetrasporangia. 
