Chroococeacew 345 



leaves and stems of submerged Mosses or Phanerogams. Each 

 cell is furnished at its upper pole with one or two long, thin 

 bristles, Avhich sometimes give off small branches or spurs near 

 their apices. The primitive chromatophore is bell-shaped, of a 

 brilliant blue-green colour, and there is a clear space in the centre 

 of the cell. Lagerheim in his original description of the genus : 

 says " nucleus singulus." The mother-cells give rise to two or 

 four daughter-cells on division. 



Many authors have placed this Alga in the Chlorophyceae, or 

 have recorded a chlorophyceous Alga under the name of ' Glceochcete.' 

 The genus as I have often found it, and as here figured, most 

 certainly belongs to the Chroococcacese. 



(.t'L Wittrockiana Lagerh. is known from several parts of the British 

 Islands, occurring as an epiphyte on Vaucheria, Cladophora, or the leaves of 

 Sphagnum. Diam. of cells 6 21 p ; length of bristles 96 260 fj. ; fig. 160. 

 GL bicornis Kirchn. has a pair of bristles attached to each cell. 



Sub-family II. CHROOCOCCE^. 



The sub-family Chroococcese embraces almost all the unicellular 

 and colonial Myxophycea?. They are unquestionably of a lower type 

 than any other of the Alga3, and some of them bear resemblance 

 to certain of the Bacteria. The cells display considerable variety 

 of form, and with the exception of the genera Synechococcus, 

 Tetrapedia, and to a certain extent Merismopedia, they are 

 enveloped in a copious covering of mucus. The mucous coat is 

 sometimes firm and lamellose, as in some species of Chroococcus 

 and Glceocapsa, but more often it is an ample, homogeneous covering, 

 very hyaline in character. It often happens that the coverings 

 of numerous cells have fused together, thus forming gelatinous 

 colonies of various sizes. Some of these colonies are large macro- 

 scopic masses, containing many thousands of cells, and possessing 

 a tough exterior. In some genera, such as Merismopedia and 

 Gcelosphcerium, the colonies are of limited size and of definite 

 shape. 



Multiplication takes place by the repeated division of the cells 

 and the final fragmentation of the original colony, each fragment 

 growing in size and repeating the processes. In the spherical 

 colonies of Cvelosphcerium a kind of budding takes place by means 



1 Lagerheim in Nuova Notarisia, 1890, p. 231. 



