usually fo u r in number. Sporangia circular, lodged in cells,
which are considerably enlarged fo r their accommodation.
Z . pellucidum Hassall, in Ann. Nat. Hist. vol. x. p. 37.
Hab. Chesliunt: A. H. H.
This is a very curious and beautiful species, and one by
no means common. 1 have only once been so fortunate as to
meet with it in a state of reproduction. In which condition it is
not possible to confound it with any other described species.
10. Zygnema r iv u la e e Hass.
Plate X X V I I . Figs. 1, 2.
Char. Filaments seven or eight inches in length, usually attached,
and in diameter about equal to those o f Z. pellucidum.
Cells varying in length from fo u r to eight times
their diameter. Spires serrated, three or fo u r in number.
Granules large.
Z . rividare Hassall, in Annals of Nat. Hist. vol. x. p. 38.
Dill. t. 4. A. B.
Hah. In the Barge, Neiv, and Lea rivers, near Cheshunt,
abundant: A. H. H. Cader Id ris : Mr. Ralfs.
This is a very distinct species, and certainly not the
Conjugata adnata of Vaucher, the filaments of which equal
nearly those of Z . nitidum in diameter. I have never been
so fortunate as to find it in a state of reproduction. I t would
not appear to be common, as I have not received it from any
other of my correspondents save Mr. Ralfs.
b. Spires two in number in each cell.
11. Z ygnema d ecimin um A_y.
Plate X X I I I . Figs. 3, 4.
Char. Filaments rather smaller than those o f Z . neglectum.
Cells twice or thrice as long as hroad. Spires two, crossing
each other. Granules large. Sporangia oval, obtuse, not
producing inflation o f the cells in which they are lodged.
Conf jugalis Dillw. t. 5 .; and C. nitida, t. 4. f. A. B.
deciminum Harvey, 1. c. p. 362.; also in Manual, p. 143.'
Hab. Cheshunt and Epping F o re s t: A. H. H. In a
pond between Ramslye Rocks and Broadwater* F o re s t;
Henfield Common; and in a pond at Hill Park, near
VV esterhaxn, K e n t: il/r, Jenner,
This is a very pretty species, and also very distinct, the
crosses described by the spires at once serving to distinguish
It from all others belonging to this division of the genus
Zygnema. Filaments frequently almost black.
c. Spires single.
12. Zygnema q u in in um Ag.
Plate X X V I I I . Figs. 1, 2.
Char. Filaments o f rather larger diameter than those o f
Z.deceminum. C d h longer than broad, performing
about three revolutions in each. Sporangia acutely oval, not
producing inflation o f the cells in which they are lodged.
Conferva porticalis Müller, Nova Comment. Petj-opolitana,
pars 3. p. 90. Conjugata porticalis Vaucher, Hist, des
Conf. pi. 5. fig. 1.; Dillw. t. 3. lower fitrure.
Hab. Everywhere common throughout Britain.
“ This conjugata, already described and observed by
Müller, IS perhaps the most common of all those of th e same
family; its spires are formed of brilliant grains united by a
thread or a tube. Müller compares them to porticos, since
in a certain state of their developement they have the form of
a semi-ellipse.”— Vaucher. The specific name of quininum
bestowed upon them by Agardh is intended to express as well
as Muller’s of porticale, which ought properly to have been
retained on account of Its priority, the form described by
each turn of the spires.
13. Z ygnema va eian s Hass.
Plate X X IX . Figs. 1, 2, 3, 4.
Char. Filaments o f somewhat less diameter than those o f