HENDERSON'S HANDBOOK OF PLANTS. 



267 



ALG 



prominent of which will be noticed in 

 their proper order. These three classes 

 are characterized by the color of their 

 seeds, which correspond for the greater 

 part with the general tint of the plants. 



1. Melanospermece, or olive-spored. 



2. Rhodospermeq?, or rose-spored. 



3. Chlorospermece, or green-spored. 



The first of these comprises the olive- 

 colored species, which, from their size and 

 abundance, are so conspicuous on our 

 shores, or which float in dense masses, 

 sometimes many leagues in extent, on the 

 surface of the ocean. On our own coasts 

 they attain the length occasionally of 

 twenty feet and more, and specimens 

 have been exhibited in New York even 

 larger than this. In the genus Laminaria 

 individuals are sometimes large enough 

 to be a load for a man; but this is noth- 

 ing to the size attained iu the southern 

 seas, or even in some parts of the north- 

 ern hemisphere. Individuals of the genus 

 Macrocystis attain the length of a hun- 

 dred feet or more, and Lessonia forms 

 submarine forests, the stems resembling 

 the trunks of trees. Some of the lower 

 species have nothing like leaves, and are 

 reduced to mere articulated threads, or 

 a shapeless mass. 



The second class comprises those 

 charming seaweeds, remarkable for their 

 elegance of form, delicacy of texture, and 

 brilliancy of color, which attract the atten- 

 tion of all wanderers along the sea-shore. 

 These are often very abundant, but they 

 seldom attain any considerable size, and 

 some of them are as delicate as Moulds. 

 The third class contains most of the small- 

 er species, in which the frond seldom as- 

 sumes the form of a membrane, but is 

 more frequently reduced to a mere thread, 

 or even to single articulations. A few 



ALG 



only are conspicuous objects, among 

 which the genus Caulerpa is most remark- 

 able, affording, on warm, sandy coasts, 

 an abundant supply of food for tur- 

 tles. Of the smaller and more obscure 

 species, in which there is often no point 

 of attachment, we have the most exqui- 

 site microscopical objects, exhibiting an 

 almost inexhaustible variety of form 

 and outline. In the two latter classes, 

 more especially, many species are so 

 marked by calcareous matter as to pre- 

 sent the appearance of corals, with which 

 productions they have accordingly been 

 arranged. A weak solution of hydro- 

 chloric acid, however, soon changes 

 the fixed carbonate of lime into soluble 

 chloride of calcium, and the structure 

 and fruit are then unmasked, and found 

 to correspond with those of true Alga;. 

 In Diatomacece, silex instead of lime is 

 imbedded in the substance of the cells. 

 Among the productions which appear 

 upon rocks exposed to the action of the 

 atmosphere, the lower Algoe are often the 

 first to make their appearance. Even the 

 cold surface of snow and ice produces the 

 bright red Alga known under the name 

 of Bed Snow, while allied species appear 

 on darker grounds. These gradually, by 

 their decomposition, afford soil for higher 

 growths.- 



The larger species of Algae afford a 

 useful though coarse article of food to 

 men and domestic animals, not to men- 

 tion the numberless tribes which they 

 support in their own element. The Laver 

 is, however, considered by many an ob- 

 ject of luxury; though, like Olives, it is 

 not in general relished at first. With use, 

 however, it is esteemed by many a most 

 acceptable condiment Many of the rose- 

 colored Algce abound in gelatine, and in 



