2o6 American Quarterly Microscopical Journal. 



have undergone a change, both in color and in feature, from 

 brown to clive-green and seruginous. These cells are filled, 

 primarily, with a homogeneous endochrome; in this are formed 

 very minute granules, the microgonidia. The cells slide out 

 from the broken or decayed end of the filament {tl d); then the 

 microgonidia enlarge and the cells assume the character of spor- 

 angia, or spore bearers {e e e e). Next, the microgonidia are seen 

 to sheath {//); they enlarge still more {g g) and divide (//). 

 Up to this period they are enclosed in an epidermis, or mem- 

 branous tegument, which now breaks, and the enclosed cells 

 are scattered (//); these in turn also grow larger and larger, 

 the internal cells divide, increase, and develop {kl/n), often 

 repeating this process many times; at last, from one of the 

 latter form (;«), Glceocapsa, here and there the young filaments 

 of Sirosiphon {n o) are reproduced. 



In this process we have a number of different forms of the 

 dubious unicellular plants which would be respectively classed 

 as Microcystis [e e e), Glceocapsa if/ggln), Glceocystis [h), and 

 Gld'othece (i i). These are often found in masses, sometimes the 

 one and sometimes the other predominating. Under certain 

 conditions the mother plant will be produced, and under other 

 conditions only the spores will be repeatedly developed. In a 

 deep mountain ravine in this vicinity, where the two forms 

 abound, the more exposed rocks are covered with growths of 

 Sirosiphon and a few of the Ghvocapsa cells, while on other cliffs, 

 which are shaded and dripping with moisture, the so-called 

 Glceocapsa forms are the most abundant, with only occasional 

 filaments of Sirosiphon^ and may be drawn off by handfulls. 

 They are evidently merely different conditions of the same 

 plant. 



Fig. 2 represents another form of Sirosiphon, found by Mr. 

 Brandegee at a soda spring in Colorado. The specimen was 

 scant, but the forms were very distinct, especially in the spores, 

 a is a sporangium, a Microcystis form, and bbb the Glceocapsa 



DESCRIPTION OF PLATE XVIII. 



Fig. I, Reproduction of Sirosiphon Alpiniis. - 



Fig. 2, Sirosiphon, n. sp. ? 



Fig. 3. Scytonenia. 



Fig. 4. Scytonema trtincicola. 



Fig. 5. Ulothrix. 



