A4 
or the movements of birds, or some other agent of 
distribution, brings about a re-colonisation of the Manx 
coast. 
When compared with other areas the algal flora of the 
Isle of Man is not strikingly rich. Despite its border-line 
position between northern and southern floras, the 
Island does not wholly share either flora since the plants 
of restricted distribution in both are missing. It is 
difficult to account for some of the absentees even on the 
view expressed above ; for example, Spyridia filamentosa 
and Bostrychia scorpioides, though frequent in the Menai 
Straits, have not yet been recorded for the Island. Nor 
does the Island flora show the richness characteristic of 
the Irish coast about the same latitude. Compared with 
the list of algae published in the Clare Island Survey, the 
Isle of Man records can show only 343 species and varieties 
against the 424 (exclusive of blue-green) of the Irish 
coast. The major portion of the algal flora therefore 
consists of species which it shares in common with the 
rest of the British Isles. 
In compiling the systematic list an endeavour has been 
made to indicate, for the benefit of the student, where an 
illustration of each species may be found, by reference to 
literature which the student will be able to consult in the 
library of the Biological Station. Most of the references are 
to the ‘“‘ Phycologia Britannica,’ which is indicated in the 
text merely as ‘“‘ Harvey.’’ The numerals in the reference 
refer to the volume and to the synoptic number of the 
species. It is frankly admitted that many of the illustra- 
tions referred to are not fully adequate; an attempt has 
been made to supply deficiencies by the inclusion of original 
drawings, but the expense involved in providing satisfactory 
illustration for all the species is prohibitive for this 
publication. 
The authors are greatly indebted to Professor Rosenvinge 
