FRESH -WATER A L U J2 OF TUE UNITED STATES. 103 



• 

 I Besides the true Zngoftpnres, Hassall many years since described bodies (Fresli- 

 water Alga?, vol. i. pp. 132, 156, 170), wliic;h he found in filaments of this family, 

 I and which resemble in all respects ordinary Zt/ijospores, but are produced each 

 in a single cell without any .aid from a second cell. He affirmed that he had 

 observed this phenomenon especially in two species, Spirogyra mirahiiis and 

 ; Zijgnema notah'dls. These observations were doubted by some, whilst others, as 

 ; Alexander Braim, supposed that there was a division of the cell protoplasm into 

 I two distinct portions, and then a conjugation of these within the original cell, and 

 that Mr. Hassall had overlooked these changes. Prof. De Bary, however, states 

 that he has seen a great many instances of this production of spores without conju- 

 gation (all in one species), and that there can be no doubt that llassall's obser- 

 vations are substantially correct, and that no division of the primordial utricle such 

 1 as was imagined by Prof. Braun takes place. Spores formed in this manner, as 

 : yet have not been seen to develop. There is, therefore, no certainty that they are 

 j capable of doing so. It is possible that they are merely the results of abortive 

 j attempts at reproduction, Avanting the power of development because not fertilized. 

 j Pringsheim and others have drawn from these bodies strong argument against 



the idea, that conjugation is to be looked upon at all as a sexual process. 

 ■ The arguments both for and against regarding conjugation as the simplest ex- 

 i pression of sexual life are ably elaborated by De Bary, Untersucliungen iiler die 

 \ FamU'ie dcr Conjugate m, p. 57, to which I must refer those desirous of following 

 the subject further, contenting myself with expressing an agreement with the con- 

 clusions there arrived at, namely, that in conjugation the first dawnings of sexuality 

 are to be found. Looking at it in this light Prof. De Bary states his conviction 

 I tliat the spores formed in the manner last described, bear the same relation to the 

 j true Zygospore that the bud of a Phanerogam does to its seed, or the Zoospore of 

 an CEdogoninm does to its resting spore. 



Quite a number of bodies have been described by the older authorities as being 



found within the cells of plants of this family, which more recent observers have 



I proven to be parasitic. Such are the " Spermatic spheres," transparent spheres 



motile by virtue of vibratile cilia, various monads, &c. «S:c., bodies for which it has 



j been claimed, from time to time, that they were sexual elements, spermatozoids. 



Genus SPIROGYRA, Link. 



CelluliB TegotativoB cylindrica;, ftisciis cliloropliyllosis si)ii-alil)us instructie. Conjugatio aut lafci'. 

 alis aut scalarilbrmis aut et lateralis et scalarifonnis. 



Syn. — Spirogyra et Bhynclionema, KiJTZiNa, Rabenhorst, et auctores. 

 Salmacis, Boet. 

 Zygnema (pavtini'), Hassall. 



Ycn;etative cells cyliiulrical, furnished with .spiral ohlorophyl bands. Conjugation cither lateral 

 or scalariforni or both lateral and scalariform. 



Bemarl-s. — The genus Spirogyra, as defined above, has been divided by Kiitzing, 



\ Rabenhorst, and others into two genera, the chai'iicters being drawn from the 



method of union of the conjugating cells; in the one case the neighboring cells of 



a single filament [lihytichoncma), in the other cells of distinct filaments {S^drogyra)^ 



