chordariacejE. 69 



The external appearance of the plants which compose it 

 does not at all betoken the very beautiful structure 

 which will be revealed when they are dissected and ex- 

 amined under the microscope. 



Leathesia tuberiformis. Tuber-shaped Leathesia. 



Fronds growing singly on other sea-weeds, or in clusters, 

 on rocks; when young, filled with fibres, becoming hollow 

 sacs as they mature, varying from a quarter of an inch to an 

 inch and a half in diameter. 



Leathesia crispa. Crisped Leathesia. 



" Frond solid; axial threads very densely crowded, simple, 

 dichotomous, with very long joints; peripheric ramuli cUxb- 

 shaped, incurved, or arcuate, submonilitorm, the joints as 

 long as broad. Spores pear-shaped. — On Ghondrus crispus." 



This species is not included in the ' Phycologia Bri- 

 taunica/ but was described by. Dr. Harvey in the ' Na- 

 tural History Review' for 1857. I have not seen a spe- 

 cimen, and have therefore taken the above description 

 verbatim from Dr. J. E. Gray's ' Handbook of British 

 Algae.' 



Leathesia Berkeleyi. Berkeley's Leathesia. 



Frond flattened, solid, the fibres densely packed. 



This plant has been found on the south-west coast oi 

 England, and in considerable abundance on the west 

 coast of Ireland. It probably grows in many other 

 localities, but its dark-brown colour, frequently of nearly 

 the same shade as the rock to which it adheres, causes it 

 to be overlooked by any but a very careful observer. 



