APPENDIX. xlix 
DESCRIPTION OF PLATE IY., 
ILLUSTRATING 
MR. ARCHER’S THREE PAPERS—ON ZYGOGONIUM AND MOUGEOTIA 
(p. 114)—ON ASTERIDIA IN PENIUM DIGITUS (p. 144), AND ON THE 
CONJUGATION OF TWO SPECIES OF SPIROTZNIA (p. 147). 
Rees i. 
12. 
Figs. 1-11 300; Fig. 12 400. 
Ordinary sterile filament of Mougeotia levis, Arch (= Zygogonium leve 
(Kiitz)? Unfortunately this figure is faulty in not displaying” the 
central nucleus in each joint. 
Conjugated state of same, showing the zygospores free in the cavity of 
the transverse tube, the “whole contents of the parent cells being 
absorbed in their formation, and not a central portion only shut off 
in a special chamber, as in Mesocarpus. 
A pair of Asteridia shown within the cavity of the cell of anexample of 
Penium digitus, a portion of the original contents of which have 
become effete and brown coloured. 
A pair of examples of Spirotzenia condensata in juxta-position for the 
purpose of conjugation ; the contents of both individualized into two 
portions, each becoming contracted into an elliptic figure, the spiral 
arrangement of the band of endochrome becoming effaced. 
The opposite masses of the contents of the original pair of parent cells 
now coalesced, and gradually assuming the globular figure and rigid 
cell-wall shown in next figure. 
The pair of zygospores having now assumed a globular figure, but not yet 
showing the honeycomb external decoration. 
The latter more advanced and coating of mucus more densely developed, 
with a sharply-detined boundary. 
The pair of zygospores more fully formed, focussed down to the equa- 
torial line, showing the honeycomb structure in side view. 
The same focussed up a little, so as to see partially into the cavities of 
the honeycomb structure. 
An empty zygospore, focussed above an equatorial line, showing the 
mouths of the cells of the honeycomb. 
The angularly-lobed zygospore of Spirotenia truncata (Arch.), the four 
half-cells of the parent pair of cells still appended. 
[Note.—By an unfortunate oversight the above Plate is referred to in the Paper on 
Asteridia in Penium (p. 144), and on Spirotenia (p. 147), as Plate VIII. in place of 
Plate IV. | 
