95 
Studies on Cyanophyceae. 
EXPLANATION OF THE FIGURES, 
1. Ordinary vegetative filament, showing intercalary lieterocysts 
and mucilage-sheath. ( x 600). 
2. Development of an intercalary heterocyst, showing the terminal 
granules and the uncontracted contents. (X1500). 
3. Terminal heterocyst, showing protoplasmic connection with 
adjoining vegetative cell. (X730). 
4. Long [filament bounded by numerous terminal lieterocysts and 
forming spores in its central portion. ( X730). 
5. Oblong intercalary heterocyst with pointed ends. ( X730). 
6 and 7. Protoplasmic connections between the vegetative cells. 
(X730). 
8a. Intercellular substance, excreted between two vegetative cells. 
(x 730). 
8b. Development of terminal heterocysts on either side of the same. 
(x 73°)- 
9. Portion of a filament with three terminal heterocysts, showing 
two adjoining cells with homogeneous contents, the last formed 
heterocyst has uncontracted contents and shows the terminal 
granule, the next shows the lip-like thickenings on either side 
of the pore, whilst the furthest heterocyst shows the plate-like 
thickening, the distinct pore and the granules in the contents of 
the lieterocyst ( x 1500). 
lieterocysts, this assumption is without much point. As yet Brand’s 
observation of the germination of the contents stands isolated ; its 
confirmation and the discovery of a similar state of affairs in other 
genera of the group would in my opinion confirm the spore-like 
nature of the lieterocysts. In these latter structures we probably 
have the remnants, of what may once have been an important 
reproductive organ of the Cyanophyceae, whose functions have now 
in great part been taken over by the spores. Under these circum¬ 
stances germination of a heterocyst may only take place under very 
extreme conditions and the failure as yet in confirming Brand’s 
observation may, as this author has himself suggested, merely be 
due to these conditions not having been attained. 
BIBLIOGRAPHY. 
hornet et Thnret (’80). Notes Algologiques. Deuxieme fascicule. 
Paris, 1880. 
Borzi (’78). Note alia morfologia e biologia delle alghe ficochro- 
macee. Nuovo giornale Botanico Italiano. 
X. 1878. 
Borzi (’87.) Le comunicazioni intracellulari delle Nostochinee. 
Malpighia. Vol. I., 1887. 
Brand (1901). Bemerkungen fiber Grenzzellen und fiber spontan 
rotlie Inhaltskorper der Cyanophyceen. 
Ber. Deut. bjot. Ges., Vol. XIX., 1901. 
