FRESH-WATER ALG^ OF THE UNITED STATES. 163 



Besides the true Zygospores, Hassall many years since described bodies (Fresh- 

 water Algae, vol. i. pp. 132, 156, 170), which he found in filaments of this family, 

 and which resemble in all respects ordinary Zygospores, 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 mirabilis and 

 Zygnema notabilis. These observations were doubted by some, whilst others, as 

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

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

 that Mr. Hassall had overlooked these changes. Prof He 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 Hassall's obser- 

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

 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 

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

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



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- 

 pression of sexual life are ably elaborated by He Bary, Untersuchungen uher die 

 Familie der Conjugatem., 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. He Bary states his conviction 

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

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

 an CEdogonium 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 

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

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

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



Genus SPIROGYRA, Link. 



Celluiae vegetativse cylindricse, faseiis chlorophyllosis spiralibus instructae. Conjugatio aut. later- 

 alis aut scalariformis aut et lateralis et scalariformis. 



Syn. — Spirogyra et Mynchonema, Kijtzing, Rabenhorst, et auctores. 

 Salmacis, Bort. 

 Zygnema (partim), Hassall. 



Vegetative cells cylinrlrical, furnished with spiral chlorophyl bands. Conjugation either lateral 

 or scalariform or both lateral and scalariform. 



Remarhs. — The genus Spirogijra, as defined above, has been divided by Kiitzing, 

 Rabenhorst, and others -into two genera, the chai^cters being drawn from the 

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

 a single filament {Rhynchonema), in the other cells of distinct filaments {Spirogyra), 



