Fritsch . Studies on Cyanopliyceae. 
213 
Gomont: Becherches sur les enveloppes cellulaires des Xostoeacees lila- 
menteuses. (Bull. Soc. bot. de France. Ser. 2. T. X. 1888. p. 201). 
Kirchner: Schizopliyceae. (Engler u. Prantl, Die natlirl. Pflanzenfam. 
Teil. I. Abteil. '1a. 1898.) 
Klebs: Über die Organisation der Gallerte bei einigen Algen und Flagel¬ 
laten. (Unters. .Bot. Inst. Tübingen. Vol. II. Heft II. 1886). 
Kolkwitz; Über die Krümmungen und den Membranbau bei einigen Spalt¬ 
algen. (Ber. Deut. bot. Ges. Bd. XV. 1897, p. 460.) 
Kiitzing: Pliycologia generalis. 1843. 
Xadson: Über den Bau des Cyanophyceen-Protoplasts. (Scripta bot an. 
Horti Universitatis Imperialis Petropolitanae. T. IV. Fascic. II. 1895.) 
(German resume.) 
Xägeli: Gattungen einzelliger Algen physiologisch und systematisch be¬ 
arbeitet. Zürich 1849. 
AVager: The cell-structure of the Cyanopliyceae. — Preliminary paper. 
(Proc. Boy. Soc. London. AMI. 72. p. 401.) 
Description of the figures on plate TU. 
(It was found necessary in many cases to use high magnihcations. — 
Zeiss's apochromatic 3,0 nun. Apert 0,95 and compensation eye-piece 12 or 
18 being mostly employed. All the figures were drawn with the help of 
an Abbe drawing apparatus. The following Symbols are made use of to 
denote different points in the figures; c. s. — cell-sheath: i. i. = inner 
investment: e. s. = external sheath; t. s. = transverse septum: ex = exo- 
spore: en. = endospore; li. = heterocyst). 
Fig. 1 and 2. Small portions of hlaments of Anabaena , stained with 
metliyl blue: the transverse septa are curiously contracted, so as to resemble 
protoplasmic Connections. (X about 2300.) 
Fig. 3. Two young cells of a species of Nostoc in process of division: 
the inner investment is not indicated, a transverse septum (t. s .) just 
appearing and cell-sheath constricted: b Division complete: cell-sheatli of 
each cell evident, being separated by the thick colomless transverse septum. 
(X about 2500). 
Fig. 4. An ordinary vegetative hlament of Anabaena in the unstained 
condition. The cells are separated by well-marked transverse septa. (> 1450. 
Fig. 5. Portion of a vegetative hlament of Anabaena , stained whth 
lodine. The cells are separated from one anotlier by well-marked trans¬ 
verse septa (t. s .) and the cell-sheaths (c. s .) are seen to be individual to 
each cell. AVithin these latter is a well-dehned inner investment (i. /.), con- 
tinuous with the transverse septa. Xote that at the lower end. which 
represents the termination of a hlament, the cell-sheath extends right round 
the one end of the cell. (X 2300 about.) 
Fig. 6. Three spores of Anabaena , showing exospore (cell-sheatli) and 
endospore (inner investment), and separated from one anotlier by a well- 
marked space. (X 1450.) 
Fig. 7. Sporogenous cell of Anabaena with contents in process of 
protrusion. The liberated portion is surrounded by a new inner investment. 
whilst the outline of the open end of the cylindrical cell-sheath raus round 
the approximate equator of tlie protoplast. (X 1450). 
Fig. 8. Small portion of tlie sporogenous hlament of Anabaena (with 
almost mature spores); the uppermost cell lias the inner investment pro- 
duced into a papilla terminally, which is plainly surrounded by the one 
end of the cell-sheath. (X 1450). 
Fig. 9. Division of a cell of Gloeocapsa. showing the transverse septum 
and the contricted cell-slieath, which is as yet not split. (X about 1600.) 
15 
Beihefte Bot. Centralbl. Bd. XYIH. Abt. I. Heft '2. 
