29. Nitella flexilis, Ag. Forma, longifolia, elongata. 



30. " flcxilis Ag. var. subcapitata, A. Br. 



31. " tcnuissima, Kittz., forma longifolia. 



32. " glomerulifera, A. Br. (N. capitata, in Halstead). 



33. " opaca, Ag. 



34. " minuta, Allen, nov. sp. 



35. Tolypella cornosa, Allen. 



36. fimbriata, Allen. 



37. " inter texta, Allen. 



38. Chara Jiydropitys, var. genuina, A. Br. 



39. " sejuncta, A. Br., forma tenuifolia. 



40. " gymnopus, var. armata, A. Br. (Sandwich Islands). 

 4oa. Nitella trtcellularis, Nordst. (from New Zealand). 



The fifth fasiculus, in preparation, will include Chara crinita, Ch. 

 hornemanni (from Florida), Ch. gymnopitys (alpha), Ch. hydropitys, 

 var. perfecta (from Mexico), Nitella morongii, Allen, and some 

 varieties of the more common species. 



Correspondence is cordially invited and the determination of 

 species will be cheerfully undertaken, particularly as a more ex- 

 tended knowledge of localities will the better enable the author to 

 give, in the second part of this work, the geographical distribution of 

 the different species. 



The second part will contain a description of all the American 

 forms, and it is intended to facilitate their determination by an illustra- 

 tion of each species. 



CHARACE^E are essentially Algae, though they cannot be included in 

 any of the groups of that class. They possess a complicated structure, 

 and in habit, as well as in the apparent distinction of parts, as stem 

 and leaves, seem allied to the Cormophytes. Reproduction is peculiar 

 and exhibits a higher development than is found in other Algoid 

 plants. The Antheridium produces swarming spermatozoids, the 

 Oogonium becomes enveloped even before fertilization, it does not 

 produce zoospores, but a resting-spore, and this, in germinating, 

 does not produce immediately the sexual plant, but an intermediate, 

 a-sexual protonema, from which the sexual plant rises as a lateral 

 sprout. 



Other Algoid plants have enveloped oogonia (Coleochaetae and 

 some of the Floridse). Some Algae even develop a pro-embryo, and 



