FUKSII-W ATKll ALUJ-: OF T II K UNITED STATES. 159 



A. converifen*, F.HRB. 



A. la- vis mediocri.s, profnndc ct an^ustu constrictus, aculcia conrcrgcntibuB armatus; semicel- 

 luli.s elliptic.!* vcl ovato-oblongis, nonnuuiiuaiu n-nitorinilius, utroque line uculuu longo Grnio 

 incurvo instruct!*. (II.) 



JUam. 0.00185" 0.0016". (U.) 



.s'yu. .t. convergena, EHRENBERU. KAIIKNIKUIST, Flora Europ., Algarum, Sect III. p. 227. 



II, ih. South Carolina; Georgia; Florida; Rhode Island ; Bailey. 



Fr.>nd smooth, l.r.'.uler than long; constriction duep, acuto ; segments elliptic, each having its 

 lateral spines curved towards those of the other; ends convex. L. 1 J 39 " jjj" B. H'TT" 

 4 J ". (Archer) 



FAMILY ZYGXEMACEjE. 



CYllulffl cylindrical osquipolnres, similes, in familias filamentosas arcto conjunct, ct cytioblasto 



mitrali plasuiule plerumquo radiunte inroluto, et plasmate chlorophylloso aut effuso, ant effigurato, 



nut i plcrniin|iie j in foscias spirales ordinato, et granulis amylaccis instructs. Filum simplex. Pro- 



io fit zyir-|Hiris conjugatione cullularum binarum ortis. Conjugatio triplici uiodo, aut latcralis 



ant scalarifonnis vcl gcnuflcxa. Vcgetatio fit divisione transversali rcpetita. 



Cells cylindrical, the samo at both ends, closely conjoined into filamentous families, furnished with 

 a central eytioblast wrapped up in generally radiating protoplasm, and with chlorophyllous proto- 

 n i tl'n-. '1 in shapeless masses or arranged in spiral filaments, and also with scattered starch- 

 prannlcs. Filament simple. Propagation takes place by means of rygospores, arising from the 

 conjugation of two cells. Conjugation occurring in three ways, lateral, scalariform, and genufloxuous. 

 tir.'M ih taking place by means of transverse division of the cells. 



/,' murk*. The family under consideration is among the commonest and most 

 widely diffused of all the fresh-water algae. In almost every ditch or spring, or 

 dripping moss-covered rock representatives of it are to be found, so that wherever 

 quirt \\iitcr is they may be confidently looked for. The single filaments are so minute 

 that 1'ivqiirntly the unaided eye cannot distinguish them, but multiplication with 

 tin-in is such a rapid process, that wherever found they are in great masses. These 

 musses, when growth is active, are of a beautiful intense green, glistening and 

 shining with the gelatinous matter which coats the threads and makes the mass so 

 sliiijM-ry. They may be found in greater or less abundance at all seasons, but as 

 tlie specific characters are largely of sexual origin, non-conjugating specimens arc 

 of little value. For this reason, Zygnemos are only worth gathering when in fruit. 

 The spores appear to be formed only in the spring and early summer, at least these 

 are the only times in which I have found fertile filaments. In this neighborhood 

 I have collected them in excellent condition as early as the beginning of April and 

 as late as the latter part of June. Further south, conjugation of course commences 

 earlier, and fine fruiting specimens received by myself from Mr. Canby were col- 

 lected in Florida by him in February. 



"When conjugating freely the mass of Zygnema or Sptrogyra loses its beautiful 

 bright green color and become dingy and even brownish, often very dirty looking. 

 The collector soon learns to pass by the beautiful vivid mass, as comparatively 

 worthless, and fasten upon the pale, wan, sickly, apparently dying specimens as 

 pri/es worthy of a place in his cabinet. 



In the Zyynemacece the individual plant, as ordinarily considered, is a filament 



