MICROSCOPICAL MEMORANDA. 159 



Mr. Bergin exhibited an instrument invented by him for the purpose 

 of illuminating transparent objects, and promised a communication on 

 the subject. 



The Society was occupied during the remainder of the evening in 

 testing the powers of Mr. Bergin's invention, and the result was deemed 

 highly satisfactory. 



Kippist on the existence of Spiral Cells in the Seeds of Acanthacea. 

 After briefly enumerating the other natural families in whose seeds spi- 

 ral cells had been previously observed, the author proceeds to describe 

 those of a plant brought from Upper Egypt by Mr. Holroyd (Acantho- 

 dium spicatum, Delile), whose peculiar appearance when placed under 

 the microscope, first led him to examine those of other Acanthacea, in 

 which family the existence of spiral cells had not been noticed. The 

 entire surface of the seed in Acanthodium is covered with whitish hairs, 

 which are appressed, and adhere closely to it in the dry state, being ap- 

 parently glued together at their extremities. On being placed in water, 

 these hairs are set free, and spread out on all sides, they are then seen 

 to be clusters of from five to twenty spiral cells, which adhere firmly 

 together in their lower portions while their upper parts are free, sepa- 

 rating from the cluster at different heights, and expanding in all direc- 

 tions like plumes, forming a very beautiful microscopic object. The 

 free portions of the cells readily unroll, exhibiting the spire formed of 

 one, two, or occasionally of three fibres, which may sometimes be seen 

 to branch, and not unfrequently break up into rings, Throughout the 

 whole length of the cell the coils are nearly contiguous ; in the lower 

 part they are united by connecting fibrils, and towards the base of the 

 adherent portion become completely reticulated. The testa is a semi- 

 transparent membrane formed of nearly regular hexagonal cells, whose 

 centre is occupied by an opaque mass of grumous matter. Those cells 

 which surround the bases of the hairs are considerably elongated, and 

 gradually tapering into transparent tubes, appear to occupy the interior 

 of the spiral clusters. Some of these appearances were noticed by 

 Delile, who described the Acanthodium in the splendid work on Egypt, 

 published by the French Institute, where also a slightly magnified figure 

 of the seed will be found, but without representing the spiral cells, 

 which Delile does not appear to have detected. 



Two species of Blepharis are mentioned as possessing a structure 

 very similar to that of Acanthodium spicatum, differing chiefly in the 

 smaller and more uniform diameter of the spiral cells, and in their 

 thicker fibre, which is always single and loosely coiled. 



The seed of Ruettia formosa on being placed in water developes from 

 every part of its surface single short thick tapering tubes, within which 

 in some cases a spiral fibre is loosely coiled ; whilst in others the place 

 of the spiral fibre is supplied by distant rings. 



In the seeds of Ruellia littoralis, Phaylopsis glutinosa, and Barleria 



