(24) 



of the teetli of these arise the receptacles, which are ovate or elhptical, 

 elevated on short stalks, attenuated to their base, generally single, but 

 often two or three from the same axil. Air-vessels very large, half an 

 inch to an inch in diameter, formed at distant intervals by the inflation of 

 the frond. Substance very tough and coriaceous, slightly adhering to 

 paper. Colour, a bright olive-gi'een, often almost dull yellow. The 

 spores are at length separable into four sporules. 



This is the largest species" of the genus that is found on our shores, 

 often reaching to the length of six or even eight feet in favourable 

 localities ; it grows the nearest to low-water of any of the genus, and 

 when much exposed to light and air loses its fine olive-green colour, and 

 becomes of a dull yellow, and changes to black when dry. 



It is readily known from all the other species of the genus by its 

 ribless or rather wingless fronds, or it would be better perhaps to describe 

 them as consisting entirely of midribs without wings. The curiously 

 stalked receptacles, arising, like the lateral branches, from the marginal 

 teeth, supply good marks of distinction ; indeed the whole habit of the 

 plant is so totally different from that of the other species, that there 

 can be no difficulty in distinguishing it. The air-vessels are very large, 

 and often explode with a sharp report under the feet of the unwary 

 collector ; and boys often amuse themselves by throwing them in the 

 fire, when the contained air, expanding by the heat, biu-sts the vesicle 

 with a loud report. 



It is perhaps the least liable to vary in its characters of any of the 

 species, with the exception of being occasionally a little more or less 

 stunted, according as it is more or less exposed to the action of the light 

 and air. 



EXPLANATION OF PLATE CXXXIX. 



Fig. 1. — Fucks nodosus, natural size. 

 2. — Receptacle cut across. 

 3. — Section of conceptacle. 

 4. — Section of. conceptacle with antheridia. 

 5. — Spores. All magnified. 



