Hodgetts. — A New Species of Spirogyra. 523 
however, on account of the H-shaped clamp, the cells are more firmly 
joined together— as stated above, one could be pushed a distance of 12-15 /a, 
or even more, before becoming actually free from its neighbour and 
probably this it is which enables the two terminal conjugation- tubes to fuse 
together and effect a firm union. 
The zygospores are lenticular in shape, being quite circular in front 
view but broadly oval in the side view (see Text-fig. 5). The wall of the 
mature zygospore is three-layered, as in other species, the outer and inner 
layers being thin, smooth, and colourless, while the middle layer is thick, 
brown in colour, and verruculose, presenting a wavy appearance when 
viewed in profile. 
The female gametangium, as shown in the photographs on PI. XXII, is 
swollen in the middle, often to a considerable extent and much more than 
is necessary to accommodate the zygospore. The only other species of the 
genus which have the female cells swollen in this way, and with which the 
species now being described might be confused on a superficial examination, 
are Spirogyra pellucida , (Hass.) Kutz., 1 and S. sphaerospora , Hirn. 2 The 
present species differs from X. pelhicida in its narrower cells, in the presence 
of the H-shaped clamps between the cells, and in the possession of (generally) 
5 chloroplasts. X. sphaerospora has a single chloroplast, smooth-walled 
zygospores which are ‘ vollkommen kugelig ’, and no H-shaped pieces 
between the cells. 
The writer considers this new species to be one of the most highly 
evolved, if not the highest, of all the known species of Spirogyra. The 
curious H-shaped connexions — not described for any other species — which 
tightly clamp the cells together, as well as the variety of modes of conjuga- 
tion, seem to support this view. At any rate the species is of particular 
interest, since it shows that the genus Spirogyra is much more plastic, both 
in vegetative structure and in methods of conjugation, than has hitherto 
been generally supposed. 
The species has been called X. colligata , on account of the cells being 
£ bound together’ by the H-shaped connecting-pieces ; and the following is 
a diagnosis of it : 
SPIROGYRA COLLIGATA, sp. nov. 
Sp. lubrica, pallide viridis, cellulis vegetativis plerumque rectis, at 
interdum spiraliter curvatis, dia metro 8-i6(-22)-plo longioribus, extremi- 
tatibus non replicatis (sed ut plurimum plus minusve alte incurvis) ; cellulis 
binis 'contiguis confibulis H-formibus, e mem bran a cellularum externa 
efiformatis, arete colligatis ; chromatophoris 5 (interdum 4 aut 6), angustis, 
1 See West, G. S. : Journ. Bot., 1899, p. 109. 
2 Hirn : Acta Societatis pro Fauna et Flora Fennica, xi, No. 10, p. 10. I am indebted to the 
late Professor G. S. West for information concerning this species, 
