THE MARINE ALG.E OF NEW ENGLAND. 11 



have shown to be erroneous views with regard to the structure and de- 

 velopment of the different species, and Harvey's three classes no longer 

 serve as a basis for classification. The Melanospermecv and Chloro- 

 spennecc are entirely rearranged, and although the Bhodospermece are still 

 considered to form a natural group, the older name, Floridece, employed 

 by Agardn, is used to designate them. The basis of classification is the 

 structure of the fruit and the organs of fructification, in the knowledge of 

 which a great advance has been made during the last twenty years. 



Cryptophyce^. — The lowest of all the algse are those which belong to 

 the order Cryptophycew, in which, as yet, the only reproduction known is 

 by means of non-sexual spores and hormogonia. Most of the species of 

 the order are bluish green, but some are purplish, brown, or even pink. 

 The bluish-green coloring matter is due to the presence of phycochrome, 

 which is a mixture of chlorophyl and phycocyanin. The last is extracted 

 by water when the algse containing it are bruised, the chlorophyl being 

 soluble in alcohol. The species of Cryptophyoecc consist of cells which are 

 usually roundish, or disk-shaped, and which are generally held together 

 by a mass of gelatinous substance which surrounds them. The order 

 is divided into two suborders, according to the arrangement of the cells 

 in relation to the jelly. The first suborder, the Chrooeoccacecc, includes 

 all the species in which the cells are either isolated or arranged in amor- 

 phous or more or less spherical masses. Some of the species of this 

 suborder are very small, and in some of the modern classifications are 

 placed with the Bacteria, in the order Protophytes. The mode of growth 

 of the Chroococcaceai is by division of the cells, first into two, then into 

 four, and so on. The masses which they form may be called colonies, 

 each cell forming a distinct individual, which is usually capable of living 

 apart from its fellows. Spores, which are known in only one species, are 

 formed by some of the cells enlarging and taking on a thick cell-wall. 

 Nothing like sexual reproduction is seen either in this or the next sub- 

 order. 



IsTosto chines. — In the second suborder of the Cryptophycece, the Nos- 

 tochinew, the cells are always attached to one another in the form of fila- 

 ments, to which the name of trichomata is given. The trichomata may 

 either be free, as in Oscillaria (PI. I, fig. 5), inclosed in a sheath, as iu 

 Lyngbya (PI. I, fig. 4), or packed in a dense mass of jelly, as in Rivu- 

 laria (PI. II, fig. 2). The cells composing the trichomata are usually 

 disk-shaped or cylindrical, but are sometimes nearly spherical. 



Besides the ordinary cells, we find in many species a second kind of 

 cell, distinguished from the others by its glassy appearance and its yel- 

 lowish or brownish rather than bluish-green color. (PL I, fig. 3, a; 

 fig. 6, b ; PI. II, figs. 1 and 2, a.) They are called heterocysts, and are 

 found sometimes scattered amongst the other cells, and sometimes at the 

 end of the trichomata, their position often serving as a generic character. 

 The reproduction of the JS T ostoch inece takes place in two ways, by Iwrmo- 



