52 DESMIDS OF THE UNITED STATES. 



D. TEUNCATUM. Breb. Plate XI, figs. 6, 7. 



Cells stont. six to eight times longer than broad, with a 

 single inflation at the base of the semi-cell, tajjering to the 

 truncate, or broadly rounded, entire, ends ; suture forms a 

 thick rim, -n-hich projects on each side. 

 Diameter 50-75 /a. 



Florida, Minnesota, Pennsylvania. 



Peculiarities of this species are the large diameter and 

 shortness of cells in comparison with the breadth ; the at- 

 tenuated ends, truncate, or broadly rounded apices, solitary 

 inflation at the base of the semi-cells and consequent even 

 sides. Florida furnished the best developed forms. 



]). RECTUM, Delp. Plate X, figs. 20, 21. 



Cells cylindrical, straight, twelve or more times longer 

 than broad ; slightly nari-ovver at the truncate apex than at 

 the base ; moderately swollen at the base of the semi-cells. 



Diameter 2.3-2S /u. 



The distinction which Delponte makes between this form 

 and D. Baculum, to which it is vei'y closely related, is, that 

 it is perfectly straight, while the former is ' ' straightish, " 

 somewhat bent, although not so represented, Plate XI. figs. 

 3, 4, Des. IT. S. The central inflations are usually larger in 

 £>. Baculum than in D. rectum. 



D. Flotowii ? Eab. A variety. Plate XI, fig. 5. 



Large, about eight times longer than the larger diameter ; 

 suture distinct ; solitary inflation at base of semi-cells ; sides 

 straight, tapering .slightly in straight lines from the center 

 to the broad truncate apex, each angle furnished with a 

 prominent tooth ; cytioderm firm, coarsely verrucose. 

 Diameter at base of semi-cell 68 /.(. ; at apex 50 yu. 



From pond on Mt. Everett, Massachusetts. A large, firm 

 and distinct form ; not identical with the described plant, but 

 it is tolerably near it. 



D. Baculum (Breb.), D. By. Plate XIY, figs. 3, 4. 



Rather long, cylindrical, straightish margins slightly ta- 

 pering towards the ends, or nearly parallel ; apices truncate, 

 rounded. Cytioderm smooth and colorless. 

 Diameter 1-1-22 fj.. 



In general form very near D. Trabecula, but smaller and 

 devoid of the terminal vacuoles. 



Ponds, Pennsylvania, New Jersey and Florida. Bailey 

 found it also In Georgia. 



