406 ALG-fli DIATOMACEiE. [Diatomct. 



unequal, the joints longer than they are broad with a transverse 

 granular yellow mass. — Lyngb. Hydroph. Dan. p. 180. t. 62. — 

 Ag. Syst. Alg.p. 5. — Conferva teniceformis, E. Bot. t. 1683? 



Parasitic on Polysiphonice, Conferva, &c. — Frequent on every part of 

 the coast in the spring-months, investing the filiform Algce with a minute 

 pulverulent covering, mostly of a green colour, but sometimes very pale 

 or even whitish. The joints are inconstant in their relative propor- 

 tions ; but are generally longer than they are broad ; sometimes fully 

 twice as long; while, on the other hand, I have seen them nearly equal. 

 In the process of drying, the colouring matter forsakes the centre of 

 each joint, leaving a hyaline cavity, which often assumes the form of a 

 gothic cross. I am inclined to think that the figure in E. Bot. was in- 

 tended to represent this plant, but it is very incorrect. 



7. D. brachygonum, Carra. (short Diatoma); filaments very 

 minute, the joints 4 — 5 times longer than they are broad. 

 Carm, MSS. 



On small marine Algce, rare ; Appin, Capt. Carmichael. — I have only 

 seen a solitary and not very good specimen of this species, which seems 

 to be distinct by its very narrow frustula. In other respects, it is nearly 

 allied to the preceding. 



8. D. feneslrdtum, Lyngb. (fenestrated Diatoma) ; filaments 

 very minute yellowish, the joints four times longer than they 

 are broad with a transverse band of granules. — Lyngb. Hydroph. 

 Dan. p. 180. t. 61. Ag. Syst. Alg.p. 5. 



In streams, intermixed with Conferva:. Appin, Capt. Carmichael. — 

 Filaments pale yellow under the microscope, with pellucid articulations. 

 Two filaments are often seen joined together length-wise, and conse- 

 quently the whole then seems to separate both longitudinally and trans- 

 versely. 



9. D. tenue, Ag. (slender Diatoma); filaments of an uniform 

 structure (not striated), the joints 3 — 4 times longer than they 

 are broad. — Ag. Syst. Alg. p. 4. Sve?isk, Bot. t. 491./. 4 and 5. 

 Grev. Crypt. Fl. t. 354. 



Pools and lakes. Northamptonshire, Rev. M. J. Berkeley. — Forming 

 a pale brownish-green stratum, on dead leaves, mosses, &c, whitish 

 when dry. The joints ultimately pass through a very curious transforma- 

 tion. 



10. D. elongatum, Ag. (elongated Diatoma); filaments with 

 a longitudinal line, the joints ten times longer than they are 



broad Ag. Syst. Alg. p. 4. Berh. Brit. Alg. p. 21. t. 6.— 



Diatoma tenue, y. Lyngb. Hydroph. Dan. p. 179. t. 61. 



Pools and ditches, "forming ochraceous masses with other Diatomacees, 

 or scattered amongst various Conferva." Rev. M. J. Berkeley. Sum- 

 mer. — The great length of the joints sufficiently characterizes the present 

 plant. Besides, " it is observable," says my acute friend, Mr. Berkeley, 

 " that in D. elongatum the division of these (the filaments) is longi- 

 tudinal— in D. tenue, transverse : or in other words, I). elongatum is 

 composed of threads coupled lengthwise ; D. tenue of a single thread." 



11. D.floccidosum, Ag. (flocculose Diatoma); filaments with a 

 longitudinal pellucid line, the joints transversely striated nearly 



