212 ULVACE.E. 



times the membrane (as in Enteromorpha} takes the form of 

 a tube, and is then very generally branched. In Bangia, 

 a genus which ought probably to be removed from the order, 

 the frond is exceedingly slender, forming filaments which 

 sometimes consist of a simple string of cells, ranged conse- 

 cutively like those of a Conferva. 



Most of the Ulvaceae are of an intense, herbaceous green 

 colour, having glassy fronds ; but a few (as the Porphyrae, 

 Bangia) are distinguished among chlorospermatous Algae for 

 a lurid purple colour. Except this difference in colour there 

 is little in structure to separate these plants from those 

 with which they are here associated. They inhabit the same 

 places, and their mode of fructification is similar. Nothing 

 can be more simple than the fructification of the Ulvaceae, 

 so far as it is known. Every cell of the frond contains its 

 endochrome, or colouring matter, and this, at maturity, forms 

 the spore. Each cell seems capable of furnishing a sporule, 

 and in many cases four sporules ; and thus from the breaking 

 up of a single ulvaceous leaf millions of new individuals may 

 arise. No wonder, therefore, that these plants multiply so 

 fast and are so widely dispersed. They are the least local of 

 all the Algae ; some of our common kinds being found wher- 

 ever any marine vegetation exists. The shores of most coun- 

 tries supply Ulva latissima and Enteromorpha intestinalis 

 and compressa; while Ulva (Prasiola} crispa is found at Spitz - 

 bergen and in the far southern antarctic lands, being one of 

 the most northern and most southern of the Algae. The spe- 

 cies require a careful study ; particularly those of the genus 

 Enteromorpha. Comparatively few of the Ulvaceae are found 

 in fresh water. The majority grow just below high-water 

 mark, forming the marginal belt of marine vegetation, but 

 the marine kinds are by no means confined to this zone, but 

 sometimes vegetate at a considerable depth, quite beyond the 

 influence of the tide. 



SYNOPSIS OF THE BRITISH (MARINE) GENERA. 



I. ENTEROMORPHA.. Frond tubular, mostly branched. 



[Plate 25, D.] 



II. ULVA. Frond leaf-like, green. [Plate 25, B.] 



III. PORPHYRA. Frond leaf-like, purple. [Plate 25, A.] 



IV. BANGIA. Frond filamentous, (mostly) purple or pink. 



[Plate 25, C.] 



