320 PROTOCOCCE^:. 



1. BOTRIDINA VULGARIS Breb. in lit. 

 Plate LXXXI. Fig. 2. 



Char. " Fronds small, spherical, aggregated, often confluent, 



green, solid, with minute globose or subangular globules." 

 " Nostoc botryoides Ag., Syn. p. 135. Palmella botryoides 

 Lyng., Hydrop. p. 205. No. 6.; Ag. Syst. p. 14. No. 5.; 

 Grev. Scot. Crypt. Fl. t. 5. No. 243. ? P. Grevillei 

 Berk., Glean, vol. i. p. 16. t. 5. f. 1. ?" Meneghini. 

 Botridina vulgaris Meneghini, in Monograph. Nosto- 

 chinearum. 



" The fronds of various sizes, rarely surpassing the head 

 of a pin, of a subspherical form, aggregated in considerable 

 quantity, cover the stems of mosses with a pulverulent 

 blackish green stratum, which Agardh first well delineated. 

 The granules in the beginning solitary, here and there affixed 

 subspherical or slightly angular, scarcely equal in their 

 greatest diameter the five hundredth part of a millimetre ; 

 gradually they increase in size, and when they have arrived 

 at the two hundredth part of a millimetre, they manifest an 

 internal granular substance ; at a later period having acquired 

 a form exactly spherical, the internal substance is seen ag- 

 gregated or collected into the centre, and the granules sur- 

 rounded by a pellucid margin. Again they increase in size, and 

 the interior granules are seen converted into vesicles filled with 

 lesser granules. These vesicles increased in number and mag- 

 nitude, the greatest dimensions of the frond being attained, 

 occupy its entire substance, and at length the diaphanous 

 margin disappears. The whole frond is then constituted of 

 vesicles closely heaped together, and enclosing in the centre 

 granules. The primitive membrane, enclosing in its midst 

 the interwoven or cellular structure, is so closely united with 

 the peripheral stratum of vesicles, that it can in no way be 

 separated from it. The last developement having been ac- 

 complished, the peripheral stratum of vesicles altogether looses 

 its granules : whether these disappear by absorption, or escape 

 outwardly, I have never been able to perceive. In this man- 



