BRITISH DESMIDIEiE. 95 



5. C. tinctum ; frond smooth, constriction producing a linear 



notch on each side ; segments elliptic ; integument reddish ; spo- 

 rangium naked, subquadrate, conjugating fronds persistent. 



Penzance and Dolgelley, /. R. Ashdown Forest and Cross-in-hand, Sussex, 

 Mr. Jenner. 



Frond very minute, smooth, smaller than that of Cosmarium bioculatum, 

 deeply constricted at the middle, the constriction causing a linear notch on each 

 side ; segments elliptic, twice as broad as long, entire. The empty frond is 

 tinged faint red or straw-colour. 



The sporangium is large in proportion to the fronds, and quadrate, with an 

 empty segment of the fronds permanently attached to each corner. Some- 

 times the fronds couple in a crossed position, when the sporangium appears 

 variously twisted or distorted. 



I overlooked this species until I gathered its sporangia near Penzance ; and 

 indeed in the growing state it is difficult to distinguish it from Cosmarium 

 bioculatum ; but it is rather smaller, the notches formed by the constriction 

 are less gaping, and the empty fronds are slightly coloured. The sporangium 

 however differs not only from that of C. bioculatum, but from all that I have 

 seen. 



Length of frond 2-3V5" ^^ ^" "^^^^ '■> hreadth ytwo '■> length of sporangium y^Vs"' 



Tab. XXXII. fig. /. a- front view of frond ; b. empty frond ; e. side view ; 

 d. transverse view ; e,f. conjugating fronds ; g, h, i. sporangia. 



6. C. bioculatum (Breb.) ; frond smooth, constriction producing a 

 gaping notch on each side ; segments subelliptic, entire ; sporan- 

 gium orbicular, spinous. 



Heterocarpella bioculata, Brebisson, Alg. Fal. p. 56. t. 7. (1835). 

 Cosmarium bioculatum, Brt'bissou in lit. {cum icone) (1846). 



Probably common. Tunbridge Wells, Henfield, &c., Sussex, Mr. Jenner. 

 Dolgelley and Penzance, J. R. Near Bristol, 3Ir. Thwaites. Near Aberdeen, 

 Br. Dickie and Mr. P. Grant. Ambleside, Westmoreland, Mr. Sidebotham. 

 Rochdale, Mr. Coates. 



Falaise, Brebisson. United States, Bailey. 



Frond very minute, about as long as broad, deeply constricted at the middle. 

 The segments, which are elliptic, are connected by a more distinct isthmus 

 than in the allied species, hence there is a wider notch on each side. The 

 endochrome is usually more dense in the centre of each segment. The empty 

 frond is not punctate. 



The sporangium is orbicular and minute and has conical spines. 



Cosmarium bioculatum chfFers from C. Phaseolus, Breb. in its smaller size 

 and more elliptic segments, which are not in apposition. 



Length of frond ^^\g of an inch ; breadth of segment y-^Vj ; breadth at 

 constriction -g-gVr- 



Tab. XV. fig. 5. a, b. front view of fronds ; c. empty frond ; d. transverse 

 view ; e, f. sporangia. 



