S04 Transactions. — Botany. 



M. thomasiana, Arclier (" Qu. Journ,," 1862). 



Doubtful. 



This plant I only mention because I have found one specimen, clearly a 

 Micrasterias, showing distinctly apiculate elevations on the surface of the 

 frond, disposed circularly about half-way between the centre and the edge, 

 and also some appearance of the median projections of Mr. Archer's species. 

 The plant, from these peculiarities, was certainly not M. rotata ; but I had 

 not then seen Mr. Archer's paper, and unfortunately also lost the specimen 

 before I could fully examine and figure it, and have never seen one since. 

 The mention of it here may induce search for it. Close investigation will 

 be necessary to distinguish it when the frond is full of endochrome, the 

 peculiar markings can only be well seen in an empty frond. But the plant" 

 when found will repay examination, being one of the most beautiful of all 

 this extremely beautiful genus. 



M. thomasiana is described and figured in the " Quart. Journ. of Micros. 

 Science," Yol. II., new series, 1862, p. 236, and plate XII. 



M. ampidlacea,'^'- sp. nov. 



Figs. 6-8. 



Frond angular-elliptic ; segments three-lobed ; the end lobe with bi- 

 partite angles ; lateral lobes bi- or trifid, distinct, deeply divided, sinuous, 

 with apices ending in three minute spines ; edges serrated. 



The end lobe is exserted, sub -cylindrical for most of its length, then sud- 

 denly broadening to the angles which are bifid with long divisions. The 

 cylindrical portion is slightly wider towards the centre of the frond. Of the 

 two divisions at each ultimate angle the outer is the longest, and the 

 inner one is not in the same plane. 



The lateral lobes are deeply divided into two or three (but more com- 

 monly two) subdivisions ; and when there are three the extra subdivision 

 is caused by the forking of that portion of the original two which is nearest 

 the end of the terminal lobe. Each subdivision is sinuous-edged ; narrow 

 at the base, then slightly widening, then suddenly contracting to a long nar- 

 row shaft ; in fact somewhat after the shape of a flask. 



The edges are serrated, and the empty frond punctate. A row of puncta 

 usuaUy follows the edge of each lobe. The apices of the lobes, and of the 

 divisions at the terminal angles, are crowned with three minute spines. 



The endochrome is bright green, extending almost to the edges. Vesicles 

 inconspicuous. 



In side view, the frond shows like two flasks set with their broad ends 

 together ; these are the median or terminal lobes, and the lateral lobes 

 show their edges in perspective. The dilation at the base of the sub- 



* This must not be confounded with Euastnivi ampullaceuvi, Ealfs. 



