EXPLANATION OF THE PLATES. 



PLATE I. 



Palmogl&a macrococca, Kutzing?* 

 (Coccochloris Brebissonii, Thwaites). 



All the figures are from specimens from the Hollenthal, 

 near Freiburg. The figures 21 28 and 113 of 

 PL II represent the conjugation of the cells, and the 

 consequent formation of the spores, as described at 

 pp. 135,202, and 285 of the text. Magnified 350 diam. 



Fig. 1. A cell with a distinguishable gelatinous envelope. 



Fig. 2. A ceU which has attained the maximum of 

 longitudinal growth. 



Fig. 3. A cell beginning to divide. 



Fig. 4. A pair of cells produced by division, the two 

 portions still in contact. 



Figs. 5 and 6. The same, but the two daughter-cells, 

 still enclosed by the common enveloping membrane of 

 the mother-cell, have already separated, without however 

 exhibiting distinguishable special envelopes. 



Fig. 7. Two cells, considerably elongated and possessing 

 special coats, enclosed by the common mother-envelope. 



Fig. 8. A cell of moderate length with two vesicles in 



* The species ot the genus Palmoglaa, established by Kiitzing, cannot be 

 certainly determined either by the characters given in the ' Spec. Algarum,' 

 or by the figures given in the ' Tabulae Phycologicse.' In the species 

 represented in our plate, the jelly-like cell-envelopes are sometimes dis- 

 tinguishable singly, sometimes not, which renders doubtful even the section 

 in which we are to seek the species. The germ-cells vary in length from 

 g'g to 5 ' n millim., average, therefore, T ^j to ^ of a line, so that the distinctions 

 founded on size, given by Kiitzing, likewise furnish no safe criterion. 

 From the variability of the characters, it is not improbable that many of the 

 species brought forward by Kiitzing, in particular P. rupestris, macrococca, 

 cesiculosa, lucida, rufescens, and crassa, will have to be combined as forms of 

 one and the same species. 



