THE OCCURRENCE OF UNLIKE ENDS OF THE CELLS OF 

 A SINGLE FILAMENT OF SPIROGYRA 



By Bert Cunningham 



Plate 10 



Wolle in his Fresh Water Algae of the United States first divides 

 the genus Spirogyra into two groups, based upon the condition of 

 the ends of the cells. In case they are rephcate as represented in 

 figure 5 they are placed in one group, while if they are plane as in- 

 dicated in figure 6 they are placed in the other. DeToni^ makes the 

 same distinction. West^ also uses this character as a means of classifi- 

 cation, but adds concerning the former "it (i. e., the replicate ends) 

 is a character which is constant for the species for which it is found, 

 although the ingrowths are not necessarily present at the extremity 

 of every cell in the filament." 



Since there are no specific cases cited by West, and since the 

 occurrence is not described by Wolle or DeToni, and since the writer 

 has found such a phenomenon occurring, it was thought to be worth 

 noting. 



The material was collected in the spring of 1917 in an intermittent 

 pool along with considerable Vaucheria. The species may be de- 

 scribed as follows: 



Cell membrane replicate at the ends in at least half of the cases 

 examined; chlorophyll band single, usually about four turns; con- 

 jugation scalariform; vegetative cell length about 200 mu, width 

 about 25 mu; zygote cell length about 175 mu, width about 40 mu; 

 zygote somewhat spindle-shaped; length 70 mu, width about 35 mu. 

 This follows so closely the description for S. spreeiana Rahb., that 

 the writer places it in this species. 



The accompanying figures illustrate more clearly than words 

 the phenomenon. Figure 1 is a diagrammatic drawing (in which no 

 effort has been made to represent the shape of the cell or zygote) 

 of a pair of conjugating filaments. Each cell is indicated as it 

 occurred in the filament. Those marked with double arrows are 

 replicate while the others are plane. Those in which we were unable to 

 determine the nature of the end we have indicated by f. Cells preparing 

 to conjugate are indicated by a P. Figure 2 is a diagrammatic drawing 



' Sylloge Algarum. 



2 British Fresh Water Algae. (1904). 



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