SOME NOETH AMERICAN DESMIDIE.E. 211 



some specimens ; in others the polar lobe has 8 or more apical teeth, and these examph^s 

 have this lobe also bordered with small spines. No small spines were seen on any of the 

 lateral lobes of this form, antl all the specimens seen had a stroni^ly and densely 

 punctate (minutely granulate) membrane. 



45. MiCRASTERiAS coNFERTA, Luud. Dcsm. Saec. p. 14, t. 1. fi^. 5. 



Var. HAMATA, Wolle, Desni. U.S. p. Ill, ])1. 38. tii?s. 3, 4. {31. hamaki, Boer^. in 

 Vidensk. Meddel. 1890 (1891) p. 31.) (Fl. XIV. %s. 8, 9.) 



Long. 80-86^; lat. 75-80^*; lat. isthm. IO'S-IIdm. 



Boergesen elevates tliis to the rank of a species on account of the peculiar polar lobe 

 and the deeper and wider incisions. The incisions of the examples we have seen are 

 certainly as narrow as those of Lundell. Wolle's figures also show the incisions quite 

 as narrow as those of the latter, although Boergesen states in his note on M. hamata — 

 " incisuras multo profundiores et ampliores." The incisions in AVoUe's figures are 

 deeper than those of the typical plant, as are those in some of the specimens we have 

 seen, but in others that have come under our observation they were no deeper. The 

 ultimate division of the lobes had two short spines rather than papillae. Thus the chief 

 character of this variety is in the form of its polar lobe, which difference is not sufficient 

 to separate it as a distinct species from M. conferta. 



All the specimens seen by us had the angles of the polar lobe more uncinate, so as to 

 bring the apices of the angles within the margin of the frond. The exterior margin of 

 each wing of the polar lobe has three teeth, and also has a pair of smaller teeth on each 

 side of the median depression. The membrane is either minutely punctate or faintly 

 scrobiculate. 



46. M. Thomasiana, Arch, in Quart. Journ. Micr. Sc. vol. ii. (1862) p. 239, 1. 12. figs. 1-5. 

 Long. 271 /u; lat. 230 /i; lat. isthm. 28 /i. Lat. : k:)ng.r=l : 1-178. 



47. M. ABHUPTA, nov. sp. (PL XIV. fig. 13-16.) M. parva, profunde constricta, sinu 



sublineari et subaperto; semicellulae late truncato-semicirculares et quinquelobae, 

 lobo jwlari late triangulari incisuris subapicalibus apertis (interdum admodum 

 curvatis basin versus semicellularum), apicibus rectis (interdum levitcr truncato- 

 convexisj, angulis profunde emarginatis (interdum non emarginatis sed apiculatis), 

 lobis lateralibus truncatis medio distincte emarginatis, angulis duobus apiculatis ; 

 a vertice visse subangulari-fusiformes, polis acutis ; a latere visae angulari-ovatae ; 

 membrana glabra vel jninctata. 



Long. 40-43 ^ ; lat. 42-49 fx ; lat. isthm. 7'5-10 ^ ; crass. 12o yu. 



Many examples of this were seen, and the characters were constant. The M. truncata 

 figured by Wolle, Desm. U.S. pi. 38. fig. 9, may belong to this species. 



Genus Euastrum, Ehrenb. 



48. E. GIGANTEU3I, Nordst. in De Toni, Syll. Alg. i. p. 1100. {Tetmemorus gigariteua, 



H. C. Wood ; Wolle, Desm. U.S. p. 92, pi. 20. fig. 6 ; Alg. U.S. p. 34, pi. 54. fig. 1.) 

 We have examined a large number of specimens of this plant, and from the character 



