404 ALGJE DIATOMACE.E. [Diatoma . 



Streams. In a rivulet on the Pentland hills, attached to sticks and 

 stones, Dr. Greville. April.— Tufted, 2 — 4 inches in length, of a rather 

 bright green hue, but pellucid and colourless under the microscope. On 

 account of its excessive fragility, it is almost impossible to obtain perfect 

 specimens. 



101. Achnanthes. Dory. Achnanthes. 



Frond stipitate, standard-shaped, composed of few frustida, 

 which at length separate, (without cohering at their angles). — 

 Name; ayyri, the froth of the ocean, and avdog, a flower. 



1. A. brevipes, Ag. (short-stalked Achnanthes); joints with 

 two coloured spots, stipes very short. — Ag. Syst. Alg. p. 1. 



Grev. Crypt. Fl. t. 295 Echinella stipitata, Lyngb. Hydroph . 



Dan. p. 210. t 70. 



Parasitic on the smaller filiform marine Algce. Appin, Captain 

 Carmichael. — Very minute, apparently covering the plant on which it 

 grows with a greenish pubescence Joints transversely linear, slightly 

 curved, pellucid, marked with two oval orange spots, at length separat- 

 ing. I have never seen more than five joints present; a single one is 

 sometimes all that remains attached to the stipes. 



2. A. longipes, Ag. (long-stalked Achnanthes); joints with a 

 single coloured spot, striated and traversed with a white band, 

 stipes long. — Ag. Syst. Alg. p. 1. — Conferva stipitata, E. Bot. 

 t. 2488. 



Parasitic on the filiform marine Algce, Enferomorpha compressa, $c. 

 Near Southampton, Miss Biddulph and Miss Hill. Summer.— It is 

 observed in E. Bot. that when recent, this plant gives almost a golden 

 hue to the Algce on which it is produced ; but, when dry, is grayish and 

 mucor-like, feeling soft like cotton. Three or four joints are generally 

 present, in the centre of each of which is a red globular spot. 



3. A. Carmichaelii, Grev. (Carmichael s Achnanthes); joints 

 plane spotless (at least when dry), stipes much elongated. 



Parasitic on the smaller filiform marine Algce. Appin, Capt. Carmichael. 

 — A very distinct species ; the joints wanting the striae -and white trans- 

 verse band of A. longipes, and the stipes is very much longer. I have 

 only seen k in a dry state, and can find no trace of a coloured spot. 



102. Diatoma. Ag. Diatoma. 



Frustida forming pseudo-articulated, ^\^\e filaments, at length 

 separating and cohering at their angles. — Name; diHro/AY}, incision, 

 from the divisions as far as the angles, which cohere. 



Frushda (or joints) rounded. 



1. D. auritum, Lyngb. (auriculated Diatoma); filaments yel- 

 low, the joints quadrate rounded with an auricle at each angle. 

 —Lyngb. Hydroph. Dan. p. 182. t. 62. Ag. Syst. Alg. p. 6. 



Parasitic on various Polysiphonice and other filiform marine Algce. 

 Frith of Forth, Dr. Greville. Spring.— I have only observed this curi- 



