14 COCCOPHYCEJS. 



The red spots are at first rounded, then irregular, soon confluent, and 

 form an expanded crust, like coagulated blood of a deep purple colour. 



Plate V'Jig- 6. a, plant natural size ; b, cells magnified 400 diam. 



GENUS 8. BGTRYDXNA. Breb. (1839.) 



Cells oblong or rounded, involved in a very thick, gelatinous, 

 partially diffluent integument, in large families, which are often 

 very numerous, enclosed in a mother cell which constitutes a 

 subglobose thallus. 



Only one species in this genus. 



Botrydina vulgaxis. Breb. in Hass. Alg. 320. 



Thallus minute, rarely larger than the head of a pin, glo- 

 bose, green. 



SIZE. Thallus from 1 -500th to l-10tli mm. ; cells '002--004 

 mm. 



Meneg. Nost. p. 98, t. 13, f. 2. Rabh. Alg. in. 37. Rabh. 

 Exs. No. 388. Hass. Alg. p. 320, t. 81, f. 2. Kirch. Alg. 

 fcchl. p. 111. 



On moist ground, trunks, moss, &c. 



" The fronds of various sizes, rarely surpassing the head of a pin, of 

 a subsphaerical 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, snbsphaerical, or slightly angular, scarcely equal 

 in their greatest diameter l-500th mm. ; gradually they increase in size, 

 and when they have arrived at the 1 -200th mm. they manifest an in- 

 ternal granular substance ; at a later period having acquired a form 

 exactly spherical, the internal substance is seen aggregated or collected 

 into the centre, and the granules surrounded by a pellucid margin. 

 j^gain, they increase in size, and the interior grannies are seen con- 

 verted into vesicles filled with lesser granules. These vesicles in- 

 creased in number and magnitude, tho greatest dimensions of the frond 

 being attained, occupy its entire substance, and at length the diapha- 

 nous margin disappears. The whole frond is then constituted of vesi- 

 cles closely heaped together, and enclosing granules in the centre. 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 development hav- 

 ing been accomplished, the peripheral stratum of vesicles altogether 

 loosens its granules ; whether these disappear by absorption or escape 

 outwardly, I have never been able to perceive. In this manner the 

 frond again obtains a diaphanous margin, but different from that with 

 which, in the beginning, it was surrounded." Nenegliini. 



Plate XI. fig. 3. a, thallns magnified 400; &, cells further magnified. 



GENUS 9. FAX.MODICTYON. Ktz. (1845.) 

 Cells oval or globose, with a very thick gelatinous integu- 

 ment, united into a filiform thallus, which is connate or anasto- 

 moses in various ways. Cell division simple or double (de- 

 cussate). Propagation by zoogonidia from the ultimate gene- 

 ration of cells. 



