8 WITTROCK, SPORES OF THE MESOCARPEZA. 
Plagiospermum, it seems to me that an approximation at least 
to a sexual difference exists, thus, that one of the conjugat- 
ing cells yields at the connubium the whole of its chlorophyll- 
coloured protoplasm, whilst the other one (and the connecting 
canal) receives it!). The former cell might thus form the 
male element, and the latter the female. 
In an earlier essay”) I have endeavoured to give a con- 
tribution to the knowledge of the spore-formation in the Meso- 
carpee. I may be permitted to recall the most essential parts 
of it. In one and the same species, Mougeotia calcarea (Clev.) 
Wittr. (Spherospermum calcareum Clev.), I made the unexpec- 
ted observation that the formation of spores can take place 
equally in the manner of Mesocarpus, Plagiospermum and 
Staurospermum, equally by tripartition, quadripartition and 
quinquepartition. Compare our fig. 15, where the spores a 
and b are formed by quinquepartition, whilst the spores c 
and d are formed by tripartition of the conjugation-cell, and 
fig. 16, where the spore is formed in the manner of Pla- 
giospermum, by quadripartition. Thus the sporocarpium ap- 
pears in this species in all its known forms, with a peri- 
carpium of 2, 3 and 4 cells (most frequently with 4). In the 
same species I observed formation of spores without conjuga- 
tion. In some isolated filaments, which had had no opportunity 
of conjugating, the single cells behaved almost in the same 
manner as if participating in an act of conjugation. They 
sent forth conjugation-outgrowths which remained closed, 
because they were met by none from other cells. Within 
each cell the chlorophyllaceous protoplasm moved into these 
outgrowths, and then a partition took place, which separated 
the chlorophyll-filled part of the cell from the other part. 
In some cases a tripartition was needed to effect this (the 
Staurospermum-type), see fig. 17; in other cases only a bi- 
partition (the Mesocarpus-type), see fig. 18. These spores 
may be calied parthenospores, as being originated by 
single cells properly designed to participate in an act of fe- 
cundation, if an opportunity had offered. 
Another instance of parthenospore-formation I have found 
in Mougeotia genuflexa (Dillw.) Ag. (= Pleurocarpus mirabilis 
1!) See M. CORNU 1. c. fig. 1 and 2. 
2) »Om Gotlands och Ölands sötvattensalger», published in Bihang till 
K. Svenska Vetenskapsakademiens Handlingar. Band. I. 1872. 
