Grevillk, oh New Diatoms. 67 



Fig. 3 represents "a portion of the outer sets of wings under 

 a higlier magnifying power, and this sketch will also serve 

 to show their position with regard to each other. I was 

 some time before I could satisfactorily account for this 

 singular character^ and it is only after a number of obser- 

 vations on other winged seeds bearing more or less on my 

 specimen that I am enabled to speak with confidence about 

 it. The separate wings seem to be formed in the manner I 

 have just described in reference to Eccremocarpus. The 

 cells of the outer layer of the testa are developed to a great 

 length, and the side walls are thickened in the same way ; 

 but the front and back walls, not being supported by 

 deposit of any sort, are ruptured at a very early stage, and 

 gradually disappear, leaving the side walls only as a sort of 

 framework or skeleton. The frequent raggedness of the 

 sides of the fibres is best accounted for in this way, and the 

 appearance of one of the inner wings carefully removed from 

 the seed (fig. 4) fully confirms this view, as it still retains 

 portions of the delicate cell- wall only partially disintegrated. 

 I had hoped that an examination of the ovules in a very 

 early stage would have shown the outer wings entire, but in 

 the only flower which I have had an opportunity of dissecting 

 the ovary was too immature to throw any light on the 

 subject. Altogether, the specimen I have described reminds 

 one strongly of the leaf of Ouvirandra fenestralis, and 

 though botanically the phenomena are not identical, it loses 

 nothing in interest by such association. 



In conclusion, I must acknowledge my thanks to my 

 friend. Professor Oliver, for the specimen from which this 

 notice is written, and Mr. TuflFen West for memoranda from 

 seeds in his own collection bearing somewhat on the present 

 case. 



Descriptions of New and Rare Diatoms. Series II. 

 By R. K. Greville, LL.D., F.R.S.E., &c. 



(Read June 12th, 1861.) 



Rylandsia, n. gen., Grev. and Ralfs. 



Frustule simple, disciform, cellulose; disc with smooth 

 rays, dilated at their base, and not reaching the centre. (No 

 umbilical lines nor hyaline area.) 



