188 



is up to 5 cm. The breadth and thickness of the margin is also variable, 

 as specimens growing in more exposed places have a narrow and thick 

 margin; on the other hand specimens occurring in more sheltered situations 

 at low-water mark have a broad and comparatively thin margin. The 

 midrib is distinct below, but often scarcely visible above especially in 

 specimens with narrow and thick margin. Bladders are usually wanting 

 in the narrower, comparatively thicker specimens, but they occur not 

 rarely in broad specimens at low-water mark. They are situated in the 



Fig. 23. Fucus infiatus L. f. typica 1 : 1,8. A broad form with bladders 



(cfr. the text). 



upper part of the frond, either on each side of the midrib as figured in 

 Fl. Danica Tab. 1127 or in the axils (Fig. 23). They are 1 — 12 cm. long 

 and 0,5 — 3 cm. broad. The receptacles are 1— 10 cm. long and 0,5 — 1 cm. 

 broad, undivided or divided into two or more divisions of varying length. 

 Sometimes only the uppermost part of the receptacle is divided into two 

 approximately triangular portions. 



The broad specimens occur at low-water mark and a little below 

 it. They are usually sterile, but I have met with fructiferous specimens 

 in July— Sept. The receptacles are 3 — 6 cm. long, undivided or divided 



