( 56 ) 



branches veiy patent or divaricate, forming a roundish sub-flabelliform 

 frond. In plants producing tubercles the branches and ramuli are more 

 or less closely pinnated with short cylindrical or slightly clavate 

 horizontal branchlets, simple, toothed, bifid or even shortly dichotomous ; 

 with these the branch is sometimes closely and regularly pectinated, at 

 other times only one or two are scattered here and there, or grouped 

 together on one side. Barren or young fronds are generally compressed 

 to the apices, and not unfrequently have some of these flattened and 

 spathulate. Substance cartilaginous, firm and rigid, not at all adhering 

 to paper. Structure : central portion consisting of longitudinal, inter- 

 lacing and anastomosing jointed filaments, with short joints occupying 

 the greater portion of the frond ; these are succeeded by rather lai'ge 

 cells, arranged in vertical dichotomous series, the ultimate dichotomies 

 moniliform, of minute coloured cells, forming the surface. Colour, a 

 dark dull brownish red. Tubercles on the pinnis terminal, or near the 

 apex, occasionally sessile on the raniiili, and apparently formed by the 

 metamorphosis of the entire pinna. Tetraspores in dense sori immersed 

 in the branches, and consisting of chains of tetraspores in dichotomous 

 vertical series. 



This singular plant is one of our southern rarities, having reached its 

 northern limit in the south of England, and even there it is by no 

 means common. Young plants have sometimes a slight resemblance to 

 Clwndrus crkpus, but are more rigid and woody. To G. mamillosa in 

 the young state it has also considerable resemblance, but the segments 

 are more patent and rigid. There is scarcely any other British species 

 with which it can be confounded. 



Its very rigid woody habit mi;st render it a striking object in its 

 native pools, where, although less brilliant in colouring, and less delicate 

 in form than some of its more attractive neighbours, its stiff shrub- 

 like fronds will serve to give variety to the vegetation, and relieve, by 

 its veiy rigidity, the uniform softness produced by the abundance of 

 more delicate forms. 



EXPLANATION OF PLATE LXXXVIIL 



Fig. 1. — Gigartina pistillata, natural size. 

 2. — Brancblet with tubercles. 

 3. — Section of tubercle. 

 4. — Spores. 

 6. — Vertical filament. 

 6. — Section of sorus. 

 7. — Tetraspores from same. All magnified. 



