of the Ui'sujidieae and Diatomcse. 5 



number of small C/o5/enff, lor the most part beginning to divide*. 

 But the certainty which can only be given by direct observation 

 of the developn)ent was altogether wanting. 



The development of four daughter-cells in the interior of 

 spores produced by the conjugation of two individiials (with 

 participation of the whole of the cell-membrane), has been de- 

 monstrated by Alex. Braunf for the Palmellaeean PahnogUva 

 inncrucocca, KUtz. (?). Closer still than this species, to the diffi- 

 cult-to-be-detined limits between Palmellaccjc and Desmidiea*, 

 stands anotlier form of the same genus, agreeing almost in ex- 

 ternal form with the PeniumJenneri, Ralfs, but one-half smaller; 

 in form and magnitude like Mesotrenium Endlicherianum, Niig.J 

 In particular individuals the chlorophyll of the contents exhi- 

 bited the arrangement described by Xageli as typical for his 

 Mesotanium, forming a band-shaped body lying in the longitu- 

 dinal axis of the cell, similar to what Alex. Braun has observed 

 in Paliiwyloea macrococca^. This form, perhaps P. pnAuberans, 

 Kiitz., occurred in many thousands of specimens on the surface 

 of water, in a vessel in which other Algse were cultivated. The 

 closely-crowded individuals of Palmo(jlt£a formed a connected 

 green film with a dry upper surface, to which the air strongly 

 adhered. Each cell contained a very distinct nucleus in the 

 centre, the diameter of which amounted to a fourth or a third of 

 that of the cell. In each half of the cell occurred, in clonirated 

 cells two, in shorter cells one, globular chlorophyll-mass, con- 

 taining starch (fig. 11), The central nucleus vanished before 

 the division of the cell (fig. 12), a new nucleus then making 

 its appearance in each half (fig. 15). The origin of the lateral in 

 the place occupied by the primary nucleus, and the subsequent 

 removal of the halves resulting from division towards the ends 

 of the cell, as occurs in Spiruff>yra\\, is altogether improbable in 

 this Palmogloea ; for not only were cells (about to divide) tem- 

 porarily devoid of a nucleus met with frequently, but the larger 

 chlorophyll-mass lying in the path of the secondary nuclei would 

 offer an obstacle to its progress scarcely to be overcome. Divi- 



* See ' Verjiingiinjr,' &c. p. 14.3 (Ray Translation, 185.3, p. 134). I 

 have also often seen such cysts, which probably belonged to Closterium 

 acerositm: in the spring of 1855, also, some which, occurring in coni])any 

 with Penium closterioides, Ralfs, and containing totally uncur\e(l indivi- 

 duals, must be referred to this plant. Closterium acerosum was not pre- 

 sent in this water. I was not successful in discovering intermediate stages 

 between them and the spores. 



t Al. Braun,Verjungung, &c. pp. 145, 351. pi. 1. fig. 42 (Ray Translation, 



iy53,pp. 13(i, 285. 1)1. 1 &2). 

 X Nageli, Einzell. Algen, p. 109. 



§ Vei^ungung, p. 350. pi. 1. fig. 11 (Ray Transl. p. 328. pi. 1. fig. 1 1). 

 II Al. Braun, Verjiingimg, p. 258 (Ray Translation, p. 240) ; Pringsheim. 

 Bau der Pflanzenzellc. Berlin, 1854, pi. 3. fig. 1 a. 



