92 BRAUN, ON UNICELLUI-AR AI.G.E. 



cell (primordial or naked cells as they are termed), scarcely 

 separated by any proper membranes, and presenting no indi- 

 cation of vegetative evolution. However this may be, it is 

 clear that these transitory generations perform the functions 

 of imperfect gonidia, destined to undergo a second di^dsion, 

 on which account, and from their close similarity in habit"^ 

 and other characters, this ambiguous section should perhaps 

 be referred to the unicellular type, though it cannot be 

 denied that a connecting link with the multicellular AJgce 

 (pseudo-unicellular) is presented in it. 



From the tmiceUular Alga, besides the jjseudo-unicellular, 

 are also to be distinguished those which are typically bi- 

 cellular, producing two heterogeneous cells, one of which 

 constitutes a thallus, the other a goniocytimn or a sporocyt'mm. 

 These plants have, it. is true, a unicellvdar thallus, but have 

 also gonocytia or sporocytia distinct from and exclusive of the 

 thallus. The simplest state, such as is exhibited in extremely 

 depauperate specimens of Vaucheria, represents a simple 

 vegetating cell, terminated above in a single goniocytium. 

 But generally a more complex bicelhilar type is exhibited in 

 those forms, the vegetating cell branching in various ways, 

 and consequently supporting several fructification-cells, which 

 differ in different cases, according as they constitute gonidia 

 and spores. In Codium but one mode of fructification (that 

 of gonidia, within a goniocytium) is known, whilst in Vau- 

 cheria, Achlya, and Saprolegnia, a double, or even threefold 

 kind of fructification may be observed. f 



The author is not acquainted with a tricelhdar type of evo- 

 lution among the true Alga; ; but in the mycetoid plants 

 analogous to Algce ,% this mode of evolution is manifested 

 very distinctly in Pilobolus,^ which is truly a tricelhdar 

 fmigillus whose thallus is divided into two cells — a root, as 

 it were, and a stem, which supports a third cell {sporo- 

 cytium) . 



* Compare, for instance, Characmm with Hi/drocT/tium, Pediasinim with 

 Hydrodidyon. 



f Tlie coniiculate ramules of Vcmcheria wliich accompany the lateral 

 sporocytia containing liypnosporcs, from the observations of Karsten (Bot. 

 Zeit., 1852, p. 86), which, liowcver, should be received with caution, the 

 author scarcely doubts to be ffuiiiori/tla, emitting lesser zoogonidia (micro- 

 gonidia). [On this point vide Pringsheim's observations, given in the 

 ' Quarterly Journal of Microscopical Science,' vol. iv.] Hence it will 

 be perceived that Vaucheria presents a triple ai)paratus of fructification. 



X Tlie mucorine Fungi, amongst M'hich Filobohis belongs, together with 

 the closely allied Suprolegnice (including Leptomitus lacteus), wlioUy agree 

 with the Vaucheriacecc (and with the Codiece) in their usually unicellular 

 thallus, and the endogenous formation of their spoies. 



§ Cohn, in Nov. Acta Nat. Curios., 23, 1, p, 492, tab. 51. 



