220 MONOCYSTE^. 



I cannot discover the necessity for the genus Ulothrix. Kiit- 

 zing's definitions of the genera JJlothrix and Sphocroplea are as 

 follow : — 



Ulothrix — " Trichoma simplex, membranaceum, tener- 

 rimum, flaccidum; cellulte gelineae, tenuissima3, hyalinaj, ach- 

 romaticEe, abbreviatfe: amylideaj delicatissimje, virides, ple- 

 rumque granuliferse, primo extenste, dein paulatim in fascias 

 transversales contractte, tandem in opseospermata quatuor vel 

 pliii'a hologonimica transeuntes." 



Sphl^roplea. — " Trichoma parenchymaticum simplex, 

 cellulffi tenuissimte merabranaceje, substantia chlorogonomica 

 demum in spermatia transeunte repletie, spermatia i^rimo 

 viridia deinceps miniate fusco : epispermio duplici, exterior! 

 filiformi, internum spiraliter investiente, cuncta in series longi- 

 tudinaliter digesta." 



The endochrome in all the species of this genus in the 

 young condition is almost uniform ; subsequently, however, it 

 parcels itself into numerous zoospores in each cell. The 

 same remark applies to all the AlgcB, which are multiplied by 

 means of zoos^oores. 



Tlie species described in this genus might with some pro- 

 priety be divided into two subgenera, in the first of Avhich 

 should be placed Lynghya zonata, L. muralis, L. virescens, L. 

 Thompsoniy and L. copulata, in which the filaments are almost 

 always attached, are of a delicate and fragile nature, of a deep 

 green colour, and delight in pure water ; while in the second, 

 Lynghya Jloccosa, L. punctalis, and L. vermicular is, should 

 be ranged, these being distinguished by characters the very 

 reverse of those just enumerated, they being rarely attached, 

 tenacious, of a dull green colour, and inhabitants of impure 

 waters. In this division L. prolijica should also find a place. 



1. Lyngbya zonata Hass. 



Plate LIX. Figs. 4, 5, 6 and 1, 2, 3. 



Char. Filaments of considerable diameter. Cells usually 

 rather longer than broad, but sometimes shorter. Endo- 

 chrome at first quadrangular, not entirely filling the cavity 



