OSCILLATORIACE^ NOSTOCHACE^. 313 



condition, present an aspect altogether different. Nearly allied 

 to the preceding, is the little tribe of Nostochacece ; which consists 

 of distinctly beaded filaments, lying in firmly gelatinous fronds 

 of definite outline. The filaments are usually simple, though 

 sometimes branched ; and are almost always curved or twisted, 

 often taking a spiral direction. The masses of jelly in which 

 they are imbedded are sometimes globular or nearly so, and 

 sometimes extend in more or less regular branches ; they fre- 

 quently attain a very considerable size ; and as they occasionally 

 present themselves quite suddenly (especially in the latter part of 

 the autumn, on damp garden walks), they have received the 

 name of "fallen stars." They are not always so suddenly pro- 

 duced, however, as they appear to be ; for they shrink up into 

 mere films in dry weather, and expand again with the first 

 shower. These plants multiply themselves, like the Oscillatorise, 

 by the subdivision of their filaments, the portions of which escape 

 from the gelatinous mass wherein they are imbedded, and move 

 slowly through the water in the direction of their length ; after 

 a time they cease to move, and a new gelatinous envelope is 

 formed around each piece, which then begins not only to increase 

 in length by the transverse subdivision of its segments, but also 

 to double itself by longitudinal fission, so that each filament 

 splits lengthways (as it were) into two new ones. By the repeti- 

 tion of this process, a mass of new filaments is produced, the parts 

 of which are at first confused, but afterwards become more dis- 

 tinctly separated by the interposition of the gelatinous substance 

 developed between them. Besides the ordinary cells of the 

 beaded filaments, two other kinds are occasionally observable ; 

 namely, " vesicular cells" of larger size than the rest (sometimes 

 occurring at one end of the filaments, sometimes in their centre, 

 and sometimes at intervals along their whole length), which are 

 destitute of endochrome, and are sometimes furnished with cilia ; 

 and " sporangial cells," which seem like enlarged forms of the 

 ordinary cells, and which are usually found in the neighborhood 

 of the preceding. There is very strong evidence from analogy, 

 that the "vesicular cells" are "antheridia" or sperm-cells, and 

 that the "sporangial cells" contain germs, which, when fertilized 

 by the antherozoids, and set free, become " resting-spores," as in 

 certain members of the family to be next noticed. 



197. Although many of the plants belonging to the family 

 Siphonacece attain a considerable size, and resemble the higher 

 Sea-weeds in their general mode of growth, yet they retain a 

 simplicity of structure so extreme, that it apparently requires 

 them to be ranked among the Protophytes. They are inhabi- 

 tants both of fresh water and of the sea, and consist of very large 

 tubular cells, which commonly extend themselves into branches, 

 so as to form an arborescent frond. These branches, however, 

 are seldom separated from the stem by any intervening partition ; 

 but the whole frond is composed of a simple continuous tube, 



