64 Linnean Society. [March 1 7, 



cells readily unroll, exhibiting the spire formed of one, two, or occa- 

 sionally 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 semitrans- 

 parent membrane formed of nearly regiilar hexagonal cells, whose 

 centre is occupied by an opake mass of grumous matter. Those 

 cells which surround the bases of the hairs are considerably elon- 

 gated, and, gradually tapering into transparent tubes, appear to oc- 

 cupy 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 with- 

 out 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 Ruellia formosa on being placed in water develops 

 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 

 noctiflora, the whole surface becomes covered with separate tubes, 

 very similar in form, but destitute of spiral fibre, and terminating in 

 a minute pore, from which streams of mucilage are discharged. 



Those of several species of Barleria, Lepidagathis, &c. are entirely 

 covered with long tapering simple hairs, which expand in water, and 

 like the rest are enveloped in a thick coat of mucilage. 



In all the foregoing species the hairs occupy the entire surface of 

 the seed, and are usually directed towards its apex, though they 

 occur often most abundantly at the edges ; in others they are only 

 found attached to a marginal ring of a different texture from the rest 

 of the seed. This is the case in Strobilanthus lupulina, Blechum 

 Brownii, and Ruellia secunda. The seeds of many plants of this family 

 are wholly destitute both of spiral cells or of any other appendages 

 possessing hygroscopic properties, such for example as Acanthus 

 mollis and ilicifolius, Dipteracanthus erectus, and several species of 

 Justicia and Eranthemum. 



