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Some Peculiarities in Spirogyra Dubia. 



Paul Weathekwax. 



A form of Spirogyra found on the campus of Indiana University early 

 in the spring of 1913 has shown, in its natural habitat, as well as when 

 subjected to new physiological conditions, some phenomena of growth that 

 are not only irregular lor Spirogyra but also seem to be confined rather 

 closely to the one species. 



The plant does not agree exactly with the description of any species 

 given in the literature available, but it conforms fairly well with the de- 

 scription given by Wolle (1) and also the one given by Collins (2) for S. 

 dubia Kg. This species, according to these descriptions, has two spirals, 

 or "more rarely three", and the fruiting cell is described as being slightly 

 inflated. The plant observed here had regularly three chloroplasts, and 

 the fruiting cells were not at all swollen. Wood (3) notes this same 

 difference in the sporangial cell and suggests other variations but con- 

 cludes that these characteristics are not sufficiently different to justify 

 the description of a new species. A form showing a physiological peculi- 

 arity similar to one shown by this plant, and probably from the same 

 general location, is identified by Pickett (4) as >S'. elongata (Berk.) Kg. 



When first found the plant formed a thin, green coating on a piece of 

 rusty sheet iron lying in running water. Most of the filamenrs were only 

 one to three cells in length and were probably developing from zygotes, 

 Imt the strik'ng thing noted was the highly differentiated basal cells (Fig. 

 ■ U by which the filaments were attached to the mud on the iron. and. 

 in many cases apparently to the rough surface of the iron itself. 



Conditions were favorable for rapid growth, and ten days later the 

 filaments were three or four inches in length and composed of many cells, 

 but still as firmly attached as would have been filaments of Cladopllora 

 lit' (he same size. The root-like basal cells had grown very much longer 

 and had assumed a variety of peculiar shapes. Their walls had thickened, 

 and their contents! wen; just beginning to show signs of decomposition 

 (Fig. 0). 



