620 MINNESOTA BOTANICAL STUDIES. 



adhere to the glass when it comes to rest, by means of a 

 gelatinous secretion. It is always seen lying upon its side. 



One spore, 7.5 mic. in diameter (PL XXXIV, fig. 8), had evi- 

 dently just come to rest. When it was observed it happened 

 that the water under the cover- glass had evaporated making 

 visible the four very short cilia. A bright pigment spot and 

 a large pyrenoid were present. Other spores whose cilia could 

 not be made out, were elongated slightly, the colorless end be- 

 coming somewhat pointed in the process. The pigment spot, 

 which in the moving spore occupied a somewhat anterior posi- 

 tion, through this act of elongation had come to lie within the 

 posterior half of the body. The spores which had made the 

 most progress in germinating had fallen off slightly in diameter, 

 but had gained in length, some measuring as much as 15 mic. 

 (PI. XXXIV, fig. 9). 



Twenty-four hours later the spores had, in the case of healthy 

 individuals, developed into two celled plants, each cell with its 

 pyrenoid (PL XXXIV, fig 10). Where the division was quite 

 recent, the pyrenoids were discovered situated side by side 

 with the new wall lying between (PL XXXIV, fig 10, 11). Fig. 

 12 affords an example of the division of a pyrenoid into two, 

 preparatory to the formation of a second wall. This filament 

 is beginning to bend, which later is seen to be characteristic. 

 Fig. 13 shows a filament of some length in which the pointed 

 colorless end still remains. In most cases the young filaments 

 at this stage are green throughout. 



Notes of the rate of growth were kept for a short time. 

 Taking the average length of spores in a mount, whose length 

 was 12 mic. before germination: at the end of the first day the 

 average length was 20 mic. ; at the end of the second day, 33 

 mic. ; at the end of the third day, 60 mic. 



On the third day branches began to appear (PL XXXIV, fig. 

 16, 19, 20). When two or more spores lie in contact with, or near 

 to each other, it is not rare for the filaments developed from 

 their germination to become closely entwined and eventually to 

 form portions of the same thallus, (PL XXXIV, fig. 21, 25), or a 

 thallus originates from a single spore (PL XXXIV, fig. 22, 23). 

 The short primary filament soon produces branches on either 

 side which in their turn also give off branches. A compact 

 plate is the result which maintains a somewhat circular shape 

 (PL XXXIV, fig. 24). Sometimes, however, as in figs. 

 25, 26, the thalli have attained a large size without yet having 

 become compacted together. Sometimes from these large 



