252 MR. MIERS ON THE STRUCTURE OF THE SEED 



the seed, and to determine whether we are right in considering it to be an arillus, as 

 doubts have been suggested on this subject by some eminent botanists. In the Glusiece, 

 this consists of an entire coating, without the smallest fissure ; it is fleshy, equal in sub- 

 stance, not very thick, and generally of a reddish or orange colour. In the Tovomitece 

 (at least I speak from observation in Tovomita and Commirhcea, and Poppig relates the 

 same of Chrysochlamys), it is slit upon the dorsal face from top to bottom, with its fim- 

 briated edges overlapping each other, so that when opened out, it appears like a flat sheet 

 with the seed attached in its centre. In the Garcmiece, the external coating is much 

 thicker, of a more fluid and mucilaginous substance, generally edible, and quite entire, as 

 in the Clusiece. Notwithstanding the different aspect and texture of this covering in the 

 two last-mentioned tribes, its nature cannot there be questioned, and it is quite fair to 

 conclude that the precisely analogous development in the Gimlets is, in like manner, a 

 true arillus. It is, however, essential to determine this point beyond cavil, because in the 

 Hypericins, Marcgraaviacece, and other orders, it has been held to be merely a thickened 

 epidermis of the testa, while in the Magnoliacece it has been assumed to be the testa 

 itself. In the latter family, where the seeds are generally suspended by long funicular 

 threads, it forms a very conspicuous development, under the appearance of an entire, 

 fleshy, scarlet-coloured covering, precisely similar to that of the Clusiece, and where in 

 like manner within it, on one side, somewhat pressed into its soft substance, is seen pro- 

 ceeding from the basal hilum to the apex a flattened raphe, the upper extremity of which 

 is lost in a fungous spot filling the cavity of a distinct aperture pierced through the 

 osseous shell, — a tunic which by most botanists has been regarded as the testa, but which, 

 by some authorities, has been held to be the inner integument of the seed, called tegmen 

 by Mirbel, and endopleura by DeCandolle. Endlicher was the first to suggest this idea, 

 which he expresses in a very ambiguous manner ; in his ' Genera Plantarum,' p. 837, he 

 states that the seeds of the Magnoliacece have, in most cases, an external, fleshy, coloured 

 integument covering a crustaceous testa, with its raphe situated between it and the testa, 

 and terminated by a chalaza in its summit, but that sometimes there is no outer integu- 

 ment, the raphe in such case being found between the testa and endopleura. In this 

 definition, Endlicher evidently designates by the term chalaza, the aperture in the sum- 

 mit of the testa, which I have called diapyle, and such misapplication of the term chalaza 

 (a word, strictly speaking, confined to the peculiar thickening of the tegmen or inner 

 integument, where it is connected with the raphe around the point in which all further 

 trace of the continuity of the nourishing vessels ceases) has probably led to the error of 

 considering the true testa to be the tegmen of the seed. In the diagnoses of the several 

 genera of the Order (at least in the tribe Magnoliece), the first-mentioned character is 

 assigned in detail to each genus in succession; but as the latter very inexact feature 

 (where the raphe is found between the testa and inner integument) is applied to no single 

 genus, it was probably meant to refer to the Illiciece*, although this is nowhere explained 

 or described. Dr. Asa Gray, however (in his • Genera PI. Un. St.' i. p. 60. pi. 23), adopts 

 and amplifies this suggestion in unequivocal terms ; stating that in Magnolia the seed is 



* On some future occasion I will state my observations upon the seeds of Drymis, which present anomalous appear- 

 ces worthy of notice. 



