444 SYSTEMATIC BOTANY. 



puscles, which, like the spermatozoids, pass through the pores of the 

 receptacle into the water. Here they become surrounded by a cloud of 

 spermatozoids (fig. 507, b), which attach themselves to the surface, and 

 by their ciliary movement cause the spheres to revolve. In the course 

 of a few minutes, usually, a cellulose membrane is formed upon the 

 surface of the globular corpuscle (by secretion from its primordial 

 utricle ?), and it becomes a cell (fig. 507, c), which subsequently ger- 

 minates, growing by cell-division (fi^. 507, d) into a new frond. 



These observations upon the fertilization of the germinal corpuscles of 

 the Algae are of extreme interest, both as offering examples of the process 

 of sexual conjunction, and as affording, like the development of zoospores, 

 beautiful illustrations of the theory of free-cell formation by the produc- 

 tion of a cellulose coat around a naked primordial utricle after it has been 

 completely separated from the parent, a phenomenon rarely met with in 

 the higher plants, where this kind of cell-formation can only be observed 

 in the interior of the parent structures, as in the embryo-sac of the 

 Phanerogamia. 



In the conjugating Algae we observe the new cell to be produced by 

 the complete union of the entire contents of the sperm-cell and germ-cell, 

 which are undistinguishable from each other. In the other kinds cited, 

 the contents of the germ-cell become converted into one or more globular 

 corpuscles, rudimentary spores ; while the contents of the sperm-cells 

 are developed into numerous minute corpuscles, usually of a spindle shape 

 (not spiral), moving actively by cilia. The corpuscles of the germ-cells 

 acquire a cellulose coat and become cells j the spermatic corpuscles dis- 

 appear after they come into contact with the nascent spores, either dis- 

 solving or becoming absorbed into the substance of the latter. 



CHABACE^E. 



Class Algae, Endl AIL Algales, Lindl. 



Diagnosis. Water plants having verticillately branched stems, 

 rooting more or less at the joints ; the stems either simple tubes, 

 or with the central tube clothed by a cortical stratum of smaller 

 tubes which grow over the internodes from the top and bottom 

 and meet so as to envelope it. Reproductive organs of two kinds, 

 found on the whorls of branches : (1) axillary oval sporangia 

 (nucules), consisting chiefly of a central cell with a cortex of spirally 

 wound tubes ending in a crown of teeth above ; and (2) little 

 globular anthericlia (globules), sessile on the branches, bursting 

 when mature into 8 triangular valves, the centre of each valve 

 bearing a stalk whence arise microscopic, jointed, confervoid fila- 

 ments, each joint of which gives birth to a 2-ciliated filamentous 

 spermatozoid. The nucules fall off, germinate, and produce new 

 plants. Illustrative Genera : Nitella, Ag. ; Tolypella, A. Br. ; 

 Lychnothamnus, E,upr. ; Char a, L. 



Structure and Life-history. The reproductive organs of this Family 

 are very distinctly characterized, and borne in a conspicuous external 



