10 KAARE MÜNSTER STRØM. 



The Alga was collected in a-horse-trough, where the water 

 was running very rapidly, so that I think the plant do not 

 freeze in the winter, even with the low temperatures noticed 

 this year, (down to 27 degrees centigrade below zero.) 



As I had brought the Alga indoors, and it was exposed 

 to some rising in temperature (presumably about 10 degrees 

 centigrade), it began to develop macrozoogonidia in very 

 luxuriant abundance. 



They were developed singularly in the cells and the cellwall 

 breaking up, they swam ahead by means of four cilia. 



The zoögonidia possessed a parietal chromoplast, a conspi- 

 cuous pyrenoid (starch-grain), and a red eye-spot (stigma). 



Fig. 1 is a branch of the specimen, fig. 2 a cell-row with all 

 the cells emptied, fig. 3 a zoögonidium escaping from the cell 

 before developing the cilia (?) ,fig. 4 a fully developed zoögonidium 

 and the rest of the figures (5 to 13) various stages in the trans- 

 formation of the zoögonidia into the small thalli, 



After swimming some short time they threw away the cilia, 

 fastened themselves to the substrate, and began rapid division. 

 The eye-spot is dissolved in the cytoplasm, but is, however, 

 often present even after the second division. 



As the zoögonidia germinate in so great quantities, the 

 rule is that the full-grown bundle of aduli Stigeoclonium individuals 

 hss originated from several hundred swarmspores. 



On October 10th, 1919, specimens of this species were collec- 

 ted in the same place. It is a matter of fact that such Algæ 

 very often survive the winter in a vegetative state, and my own 

 experience is that perhaps the greater number of Algæ pass the 

 winter without producing resting- spores. 



Here is an interesting field of investigation and very little 

 attention has been paid to it in the past, most authors 

 simply thinking, that all the Algæ developed restmg spores of 

 some kind in the autumn, and passed the winter in that state. 



In many cases it is true, but I think oftener it is not so. 



