io HANDBOOK: OF SEA- WEEDS. 



duce themselves by the union of two endochromes. They are 

 very interesting objects under the microscope, owing to the 

 spiral or zigzag arrangement of the endochrome of many of 

 them, and the delicacy of all. 



The Bulbochseteos constitute a small group, some half-a-dozen 

 species being British. They are freshwater plants, composed 

 of articulate branched filaments, with fertile bulbshaped 

 branchlets. The endochrome is believed to be fertilized by 

 bodies developed in antheridia, the contents of each fertilized 

 cell dividing into four ovate zoospores. 



The last two groups of green sea-weeds consist chiefly of 

 marine plants. Of these the first, Siphonese, is so called because 

 the plant, however complicated, is composed invariably of a single 

 cell. It propagates by minute zoospores, by large quiescent 

 spores, or by large active spores clothed with cilia. It includes 

 the remarkable genus Codium, three species of which inhabit 

 the British seas. In Codium Bursa the filamentous frond is 

 spherical and hollow, presenting more the appearance of a 

 round sponge or puff-ball than a sea-weed, and is somewhat 

 rare. Another species greatly resembles a branched sponge, 

 and the third forms a velvety crust on the surface of rocks. 

 Another genus, Vaucheria, is of a beautiful green colour, form- 

 ing a velvety surface on moist soil, on mud-covered rocks over- 

 flowed by the tide, or parasitic on other sea-weeds. The most 

 attractive plants of this family are however those of the genus 

 Bryopsis, two of which are found on the British shores. The 

 most common one is B. plumosa, the fronds of which grow 

 usually in the shady and sheltered sides of rock pools. 



The fronds of the last of the green-weed groups, the Ulvacese, 

 are membranous, and either flat or tubular. Two of them, U Iva 

 latissima, the green, and Porphyra laciniata, the purple laver, are 

 among the most common sea- weeds, growing well up from low- 

 water mark. The propagation in all of them is by zoospores. 

 An allied genus, Enteromorpha, is protean in its forms, which 

 have been classed under many species. They may, however, be 

 reduced to half a dozen. Some of them are very slender, so as 

 almost to be mistaken for confervoid plants. 



With the Rhodospermerc we enter a sub-order of Algce, ex- 

 clusively marine, the plants in which have always held out great 

 attractions to the collector. In structure they are expanded or 

 filamentous, nearly always rose-coloured or purple in colour. Of 

 the fourteen groups into which they are divided by Harvey, the 

 first is Ceramiaceas, articulate Algae, constituting a large propor- 

 tion of the marine plants of our shores. Of the genus Ceramium, 



