27 



Conjugation of Diatom: Orthoneis binotata Grunow. 



By T. H. Buffham, A.L.S. 



(Read Feb, 19, 1892.J 



Plate III. 



The valve of this marine diatom is elliptical, axes of the 

 ellipse as 4 : 3, with a median raplie, central and terminal 

 nodules, and a more or less indistinct stanros. The transverse 

 rows of dots are straight near the centre of the valve, and 

 curved as they approach the extremities, about 40 in '001 inch 

 (=16 in -01 mm.). These cover the whole of the outer surface 

 of the valve. Viewed from the inner side there is seen to 

 project from each lateral edge of the valve a semi-elliptical 

 plate which reaches about half way towards the raphe. The 

 plate has a length of about half that of the valve, and one- 

 fourth that of its breadth. Although a prominent feature in 

 every view of valve or frustule its structure is not easy to define. 

 It appears, however, to be irregularly nodulose, and thicker and 

 much less translucent than the valve (Fig. 5). Having seen a 

 valve with both plates broken off, but yet with very little of the 

 edges of the valve deficient, and after carefully focussing on the 

 perfect valve, I confidently offer Fig. 6 as a representation of 

 an ideal transverse section of the valve. 



It is, however, the living plant that is more interesting. I 

 cannot learn that it has been observed in this country in this 

 state, nor are there any figures extant. I first saw it adhering 

 to a' small specimen of GeramiuTn grcecillimum Griff, et Harv. 

 collected at Brighton in Sept. 1884, but the diatoms were not 

 numerous. Since then I have observed it not infrequently in 

 small numbers on filamentous algae, usually on the older por- 

 tions. But at Swanage in Aug. 1890 it was growing on 

 Calothrix conforvicola Ag. in sufficient quantity and in a state of 

 conjugation so as to permit of more extended study. 



The frustule is contained in a hyaline, gelatinous mass, of 

 symmetrical figure. Viewed laterally (i.e., what is usually 



