SOME NOKTH AMEKICAN DES.MIDIEJ:. 253 



Var. CAXADENSE, Josh, in Journ. Bot. xxiv. (1885) p. 34, t. 254. fig. 6. (PL XVI. 



%. 2.) 



Long. s. spin. 85 /i, c. spin. 110 ^i; lat. s. spin. 61-625 ^t, c. spin. 81M)7 a* ; l:it. istlun. 

 18-5 (u ; crass, s. spin. 50 fx, c. spin. 75-80 n. 



Tiie form seen by us was very symmetrical, with straight spines ; the vertical view was 

 subhexagonal. 



Var. JoHNSONii, nov. var. (X aMUopceitm, var., N. L. Johnson, in Bull. Torr. Bot. 



Club, xxvii. (1891) p. 289, pi. 211. %. 1.) 

 This form lias been noticed by us frequently. 



l^ig. 2. Fijj. a. 



Eig. 2. — XantJiidiunt antihpceum, var. minneajyoliense, WoUe. — Central spine and granules, 520/1. 

 Eig. 3. — Xanihidium cristatum, var. uncinatum, Breb. — Central granules. 520/1, 



94 XANTHiDirM CEiSTATUM, Breb. in Ealfs, Brit. Desm. p. 115, t. 19. %. 3 a-c. 



An illustration is given of the variability of the central granules of var. uncinatum, 

 Breb. (fig. xylogr. 3). 



One rather abundant American form of this species is that described and figured by 

 W. B. Turner (Freshw. Alg. of E. India, p. 99, 1. 12. fig. 28) as " X bisenarlum, Ehrenb. 

 (=X ctnslatum, var. imcinatum) var. rotundalum^ Turn.*' 



95. X. FASCicuLATUM, Elircub. ; Balfs, Brit. Desm. ex parte t. 19. fig. L 



Var. OEONENSE, nov. var. (PI. XV. fig. 25.) Var. semicellulis semicircularibus, spinis 

 brevioribus, ad angulos inferiores spinis interdum tribus et intra angulos inferiores 

 papilla instructis. 

 Long. s. spin. 57"5 yti, c. spin. 71 ^ ; lat. s. spin. 48 /u, c. spin. 61 /a ; lat. isthm. 1 1"5 ^ ; 

 crass. 25 ^u,. 



Sab. Orono, Maine. 



96. X. TETRACENTKOTUM, Wolle, Desm. U.S. p. 95, pi. 22. figs. 8, 9. (Pi. XV. fig. 2i.) 

 A specimen of this was seen that had but a single spine at one of the basal angles ; it 



exactly agreed in the form of its front and vertical views with Art hrodesmus incrassatus^ 

 Lagerh. in Ofvers. Sv. Vet.-Akad. Eorh. (1885) n. 7, p. 242, t. 1. fig. 18); his Arthro- 

 desmus, however, has but one spine at each of the basal angles ; yet we consider it is 

 but a form of this Xanthidimi, as the thickened scrol)iculate portion in the centre of 

 the semicells was the same in our plant as in his. 



Long. 41 /x ; lat. s. spin. 36'5 /z, c. spin. 54-57 /x ; lat. isthm. 12 ^ ; crass. 23 /a. 



Another example had one semicell bearing but a single spine on each side ; the other 



SECOND SERIES. — BOTANY, VOL. V. 2 N 



