OF THE DESMIDIE.i:. 721 



[Pro msionally included. ] 

 Cells elongate, attenuated, entire, aggregated into faggot-like bundles... AxKisTRODESjrus. 

 Cells rounded, compressed, deeply constricted, stipitate Cosmocladium. 



" Eiiastrum cuneatum would be represented bj a 

 Eua strum piniiaium, 

 Euastrum oblongum, 

 Micrasterias denticulata, 

 Euastrum pectinatum, 

 Tetrachastrum 



The following contractions are employed, which may require explanation : — 

 f. v., front -snew ; s. v., side view ; e. v., end view ; tr. v., transverse view ; 

 e. f., empty frond; L., length, B., breadth, of frond. The measiurements are 

 expressed in so many fractions of inch by the use of two acute marks, thus, 

 L. 1-598" = length of frond 5-^th of an inch. In most of the foreign species 

 we are without the data to give measurements. G.B., Great Britain ; I., Ire- 

 land ; F., France ; G., Germany ; U.S.A., United States of America, refer- 

 ring to the record of the occuiTence of the species in those countries. It is 

 behoved that even this rough attempt at an indication of the distribution of 

 these organisms may not be altogether without its use. Doubtless many occur, 

 and perhaps different forms, in other countries of Europe ; and information 

 is much wanted in this respect as to other parts of the world. 



Where a species occurs under another name in the works above cited, we 

 have, as far as possible, given the s}Tionym, but should it occur there under 

 the same name, it is not repeated. 



The characters printed in italics are such as immediately distinguish each 

 species from its nearest aUies, and, the genus being known, are probably 

 those which should be first consulted ; but it is always requisite to peruse the 

 whole of the characters applicable to each species and genus, with a Wew to 

 render the identification accurate. 



A. Plant an elongated jointed filament. Sporangia orbicidur, smooth. 

 1. Joints many times longer than broad. 



Genus GENICULARIA (De Bary). — Filament cylindrical ; joints elongate, 

 cylindrical, without a constriction or inflation, ends truncate ; endochrome 

 arranged in two or three spiral hands upon the cell-waU, sometimes irregular. 

 Joints previous to conjugation disunited, and bent during the process ; spo- 

 rangium placed between the empty conjugated joints. 



Gexicularia sjjirotcema (De Bary). rangiiim orbicular, smooth, placed be- 

 — Joints ten or twenty times as long '\ tween the conjugating joints, which are 



as broad, very slightly enlarged towards 

 their ends, on the outer smface rough 

 with minute scattered gi-anules. Spo- 



bent into a knee-shape, with which it 

 remains for some time in connexion. 

 "B.l-130"'-1-100.""' (m. 3.) G. 



Genus GOiN'ATOZYGOTs'' (De Bary).— Filament cylindrical ; joints elon- 

 gate, slender, cyhndiical or narrow-fusiform, mthout a constriction or in- 

 flation, ends truncate ; endochrome a single, central, longitudinal, undtdatory, 

 contracted hand. Joints pre^sious to conjugation disunited, and during the 

 process bent into a knee shape ; sporangium as last. 



GoNATOZYGON i?r///s?V (De Bary)- — I what dilated, ten to twenty times as 

 Joints ci/lifidrical with the ends some- | lonsr as broad, rough on the surface v.ath 



a A 



