Chlorophycece 51 



presence of a pigment termed by Lagerheim phycoporphyrin 1 , 

 This violet colour occurs normally in Ancylonema Nordenskioldii 

 Berggr., Mesotcenium violascens De Bary, M. purpureum W. & 

 G. S. West and Mougeotia capucina (Bory) Ag., and under excep- 

 tional circumstances it is found in various species of Zygnema, 

 Spirogyra and Desmids. The VolvocaceaB and the zoogonidia and 

 gametes of other green Algae possess vibratile cilia, which are very 

 variable in their length, number, disposition, and symmetry ; and 

 in certain of the same forms contractile vacuoles are present. In 

 the genera Tetraspora and Apiocystis ' pseudocilia ' are found, 

 which do not possess any power of movement. 



A single nucleus is present in the cells of all the green Alga? 

 except the ccenocytic and incompletely septate forms, and during 

 the formation of asexual non-motile spores, zoogonidia, or gametes, 

 it undergoes divisions corresponding to the divisions of the proto- 

 plasm. In some green Algae mitotic division of a more or less 

 complex character has been observed 2 . 



The cell-wall is very variable and its structure is often difficult 

 of observation. In the formation of a cell-wall such as after the 

 quiescence of a zoogonidium, it is developed on the outer surface 

 of the protoplasm as the result of more or less complex processes. 

 The young cell-wall usually consists of cellulose, but sometimes 

 equally of pectose. Under the action of strong acids or other 

 hydrating reagents an ordinary thick cell-wall will swell up and 

 show traces of lamination. Each lamina represents successive 

 layers of growth in thickness and in most plants consists of a 

 mixture of cellulose and pectose constituents in variable propor- 

 tions. In the Chlorophyceae these two constituents of the cell- 

 wall are differentiated while the wall is very young. They exhibit 

 considerable differences in their behaviour with reagents, the 

 cellulose constituents giving a violet colour with chlor-zinc-iodine 

 (Schulze's solution), whereas the pectose constituents do not. In 

 many Algae the pectose constituents of the cell-wall are in the 

 form of gelatinous layers on the outside of inner layers of cellulose. 

 This mucilaginous material stains readily with aniline dyes such 



1 Lagerheim in Vidensk.-Selsk. Skrift., I mathem.-natur. Kl., Kristiania, 1895, 

 no. 5. 



2 Observed in Spirogyra by Mitzkewitsch (Flora, Ixxxv, 1898) and C. van 

 Wisselingh (Bot. Zeitung, Ivi, 1898 ; Flora, Ixxxvii, 1900) ; in Chlamydomonas by 

 Dangeard (Le Botaniste, vi, 1899) ; in Closterium by Klebahn ; also in Botry- 

 dium, etc., etc. 



4 2 



