the Great Belt south of Kerteminde the minimum depth of its occurrence is 6,5 m, 
in the western Baltic Sea it is 5m and in the Sound south of Helsingør 10 m. 
In the inner Danish waters P. elongata appears in more slender forms which, 
however, are closely connected with the typical form by intermediate forms. In the 
Fig. 360. Fig. 361. Fig. 362. 
Polysiphonia elongata f. ty- Polysiphonia elongata f. Schuebelerii, from Polysiphonia elongata f. Schuebelerii, from 
pica (from Frederikshavn). Bolsaxen). A, portion of frond showing peri-  Bolsaxen). A, portion of plant with tetra- 
Portion of tetrasporiferous central cells and cortication. 70:1. B, trans- sporangia. B and C, transverse sections of 
plant. 75: 1. verse section of stem not yet corticated. 200: 1. tetrasporiferous joints. A 95:1. B, C 200:1. 
Great Belt (Sb) a form agreeing exactly with P. Schuebelerii Foslie (see above) has 
been met with in several places in 6,5 to 19 meters’ depth. It differs from the typical 
form principally in the longer joints, being up to 4 times as long as broad or longer 
where the cortication begins, and in the feebler cortication which entails a smaller 
diameter of the main axes (300—660 u). The first cortical cells are comparatively small 
and cut off by oblique walls. The pericentral cells occupy a great part of the trans- 
verse section of the old stem; they produce no new pits or a small number of multiple 
pits in the transverse walls. On the other hand, in some cases I found the central cell 
