SOME iS^OETll AMEKICAN DESMIDIEJ:. 239 



Long. 155^; lat. (cum spin.) 142^; lat. isthm. 27^. (PI. XIY. fig. 1.) 



Sab. Harvey Lake, Lycoming Co., Pa. 



We agree with Lagerlieim (in Ofvers. Sv. Vet.-Akad. Eorh. (1889) n. 8, p. 53G) that 

 Micrasterias Kitchelii, WoUe (Desm. U.S. p. 116, pi. 37. figs. 1, 2), belongs to this 

 species ; it is larger and has distinctly produced angles, a shorter polar lobe, and a more 

 open sinus; it should be called var. Kitchelii, nobis. 



89. Micrasterias furcata, Ralfs, Brit. Desm. p. 73, t. 0. fig. 2. 



North American forms of this species are very variable with regard to the division of 

 the lateral lobes. Mr. N. L. Johnson, in Bot. Gaz. vol. xix. (1894) pp. 58-00, pi. 6. 

 figs. 7-14, writes upon this variability, and after examining a large number of specimens 

 showing these variations we agree with him that M. pseudofurcata, Wollc (Desm. U.S. 

 p. Ill, pi. 35. fig. 4; M.furcata var. decnrta, W. B. Turn, in Journ. Boy. Micr. Soc. 

 (1885) p. 934, pi. 16. fig. 10), and M.furcata var. simplex, Wolle (Alg. U.S. p. 40, pi. 59. 

 figs, 6, 7), are but forms of the species. This variability applies only to North American 

 forms so far as our own observations go, 



A peculiar densely punctate form (long. 127 /i, lat. 115-120 /i, lat. isthm. 26 /i) was 

 seen in which the superior lateral lobe on one side was divided at right angles to the 

 plane of the plant, while the corresponding lobe on the other side was divided in the 

 usual way ; but the superior lobelet was again divided at right angles to the plant, these 

 latter divisions not being forked. (PI. XIV. tig. 3.) 



Another peculiar form (long. 217 ju, lat. 211 ^i, lat. isthm. 20 m) is figured (PI. XIV. 

 fig. 2) which approaches M. dichotoma, Wolle ; it is in fact an intermediate form 

 between the latter and M.furcata. The M. dichotoma, Wolle, figured by Lagerheim 

 (in Ofvers. Sv. Vet.-Akad. Porh. (1885) n. 7, p. 231, t. 27. fig. 4) appears to connect this 

 form with that figured by Wolle. Is not 3f. dichotoma an extreme form of M.furcata ? 



M.furcata forms : — 



Long. 125-151 ^. : lat. 111-139 ^t ; lat. isthm. 17-23 ^. 



M. pseudofoircata forms : — 



Long. 150-153 iu ; lat. 140-142 fx ; lat. isthm. 15-16*5 ,u. 



40. M. NoRDSTEDTiANA, Wollc, Dcsm. U.S. p. 113, pi. 52. figs. 3-5. 

 Long. 134-191 ^l ; lat. 115-171 h- > lat. isthm. 14-27 /.. (PL XIV. fig. 4.) 



After carefully noting many specimens of this we find that the " short conical 

 prominence " on the middle of each side of the exserted neck of the polar lobe varies 

 from a small conical prominence to short processes similar to the shorter ones at the 

 apex of the polar lobe, but only two thirds their length, and furnished at the apex with 

 from 1 to 3 small spines. Some specimens had these lateral projections doubled. 



41. M. MURICATA, Bail. ; Wolle, Desm. U.S. p. 118, pi. 36. figs. 4-7. 



Specimens of this were observed in which the central one of the three basal processes 

 on each side was again divided in the plane of the Micrasterias (long. 163-172 ^ ; lat. 100- 

 104 u ; lat. isthm. 18-20 ^). (PL XIV. tigs. 5, 6.) 



2l 2 



