Although the hypnospores of a species belonging to the 
family of Mesocarpex were known already to DILLWwYyN, in the 
beginning of this century, and although numerous other algo- 
logists, such as OC. A. AGARDH, G. H. K. THWAITES and ÅL. 
Braun, have later observed and described the spores of se- 
veral species belonging to this family, it was not till as late 
as the 6:th decennium of this century that the spores of the 
Mesocarpee were known as to their origin and the history of 
their development. The merit of having explained these 
things is due to A. pE Barry, who has in his excellent 
work »Untersuchungen iiber die Familie der Conjugaten» 
(1858) given a detailed description of the course of the con- 
jugation and of the formation of the hypnospores in species 
belonging to three of the genera of Mesocarpew, namely Crate- 
rospermum Al. Br., Mesocarpus Hass. and Staurospermum Kirtz. 
On account of the essential differences as to conjugation and 
formation of hypnospores shown by those groups when com- 
pared with the genera Zygnema and Spirogyra, DE BARY remo- 
ved them from the old family of Zygnemecw Menegh., in which 
they had before had their place, and regarded them as types 
of a separate family, Mesocarpece; which separation has gamed 
deserved approbation by all later investigators. 
DE BaryY's exposition of the course of the conjugation 
of the Mesocarpee is shortly this!). Two cells grow to- 
gether in the common manner by conjugation-outgrowths, 
and a resorption of the double septum between the two 
conjugating cells takes place. By this a cruciated or H-shaped 
»double cell» is formed, in which at first no other change 
takes place, than that the canal of conjugation is somewhat 
widened and that the chlorophylleoloured part of the con- 
tents of the double cell moves into the canal of conjuga- 
tion and into the parts of the double cell nearest to the 
canal. This cruciated or H-shaped cell thus formed im- 
1), Compare DE. BARY 1. c. p. 19, 21, 22 and 70: 
