BRAUN, ON UNICELLULAR ALG^E. 14<0 



they constitute, as it were, tunicated gonidia; in their germi- 

 nation, rupturing and throwing off the envelope (exosporium) . 

 Quite inert and dormant, as it were, they retain their vitality 

 until the proper period for their germination arrives. But 

 that the male function is also not incongruous with the form 

 of a spore is shown in the pollen of phanerogamous plants, 

 which is directly subservient to fecundation ; and in the 

 microspores of the Lycopodiaceae and Rhizocarpese, from 

 which fecundating spermatozoidia are produced. 



Sjpo?'es and gonidia, thus defined, agree in this, that they 

 arise from an endogenous and a free formation of cells."^ 

 The acrogenous propagative cells constitute a series differing 

 from both, which, formed at the summit of the supporting 

 cell,t and at length proceeding to form an articidated series 

 of cells, might be generally termed conidia. These occur 

 very rarely in the class of Alg8e,J but are extremely common 

 and of varied construction in the Lichens and Fungi ; some 

 being very closely allied to vegetative cells {conidia, from the 

 mycelium of Fungi), some assuming the nature of spores, 

 whilst others, again, are analogous, in a certain sense, to 

 spermatozoids ; that is, they do not germinate, and the 

 author is not aware that they are subser^dent to fecundation 

 {spermatia) of Lichens and Fungi. 



The author proposes the following conspectus of these 

 organs, based upon the foregoing considerations : 



A. A series of gonidia {macrogonidia and microgonidia, according to their 

 size in the same species); protogonidia, deiUerogonidia, telogonidia, 

 if transitional generations of gonidia exist : 



(I. Ooiiidia immotile, in tlieir nature very closely approximating vegetative 

 cells (aU germinating without fecundation) ; Phytogonidia : 



* In the ultimate generation of cells, naked : Olceocapsa, Oscillaria, 

 Scytonema, Mastichonema, Zoogkea (the gonidia of Zooglcea, 

 though tremulous, have no vibratile cilia) ; 



** Formed by the division of the contents of a single cell : Sce?ie- 



desmus, Ccelasfrum ; 



* By a free cytogenesis, though in the widest sense of the term, the 

 sense in which it is very recently defined by Priiigsheim in his observations 

 on the structure and origin of the plant-cell, who comprehends under the 

 term "free cytogenesis," every formation of cells arising without inflexion 

 of the cytoderm and from the contents alone. (Pringsh., ' Unters. iib. d. 

 Bau u. die Bildung der Pflauzenzelle,' 1854, p. 62.) 



I In what way these are formed, whether by a process of division, or 

 by the coalescing of a free cell with the parent utricle, demands further 

 inquiry. 



