Lillcy : NITELLA BATRACIIOSPERMA IN MINNESOTA. 81- 



theridium is very similar to that of Nitella flcxilis. It can be 

 distinguished very early in the growing point by its position and 

 size. It is at first a large spherical cell having a large nucleus. 

 The first division after the stalk cell is cut off is vertical (PL 

 XVIII., Fig. 16]. The second division is transverse (PI. 

 XVIII., Fig. //). The unfolding of the walls is seen in the 

 sixteen-celled stage (PI. XVIII., Fig. 12). The shields in the 

 mature state are hyaline and contain few chlorophyll bodies and 

 little coloring matter, so that the contents can be easily made out 

 in optical section. Mature antheridia are 135 by 210 mic. in 

 diameter. 



Oogonium. The oogonium arises at the base of the anthe- 

 ridium and takes the place of a leaflet. But one oogonium is borne 

 on a leaf. All stages of development can be found on the same 

 plant. Two " Wendung-zellen " were observed in N. batra- 

 chosperma (PL XVIII., Figs, j and 8]. The filaments sur- 

 rounding the egg and crown cells are colorless and hyaline. 

 The oosperm is almost spherical (270 by 300 mic.). It is of a 

 rich, golden brown color. 



BIBLIOGRAPHY. 



Migula, W. Die Characeen, in Rabenhorst, Kryptogamen Flora, 



184. 1897. 

 Pieters, A. J. The Plants of western Lake Erie. U. S. Fish Comm. 



Bull. 64, 78. 1901. 



DESCRIPTION OF PLATE XVIII. 



Figure I. Photograph of Nitella batrachosperma. Twice natural 

 size. 



2. Rhizoid showing " stocking- foot " cells with branches, X 300. 



3. Outline drawing of fertile leaf showing tip of first division bear- 

 ing antheridium and oogonium, x 300. 



4. Apex of leaf bearing antheridium, oogonium and leaflet, x 150. 



5. Apical cell of branch showing three nodal cells, X 300. 



6. Apical cell of branch showing nodal cells and last internodal 

 cell, x 300. 



7. Young oogonium showing first Wendung-zelle and first di- 

 vision of crown cells, x 300. 



8. Young oogonium showing two Wendung-zellen and two cells of 

 the crown, x 300. 



9. Membrane of oogonium, much magnified. 



