AND PECULIAR FORM OF THE EMBRYO IN THE CLUSIACE.E. 253 



exarillate, and he denominates the scarlet-coloured external tunic the testa, which pre- 

 ceding botanists have considered to be the arillus, while the hard crustaceous shell, called 

 testa even by Endlicher, is designated by him as the tegmen. This he infers from the 

 fact of having observed spiral vessels in the placentary attachment of the ovule {toe. cit. 

 fig. 7), which he thinks " clearly demonstrates that the baccate exterior integument of 

 the seed is formed of the primine of the ovule, and therefore is not an arillus*." Had 

 this distinguished botanist actually traced the growth of this last-mentioned tunic in its 

 different stages, from the primine of the ovule, he would have established an inexplicable 

 fact, but this he does not appear to have done ; simply therefore because the primine is the 

 more exterior tunic of the ovule, and the arillus is the outermost coating of the seed, it 

 does not necessarily follow that the one is the product of the other ; and notwithstanding 

 the argument of Dr. Gray, there is little reason to doubt that in Magnolia the scarlet 

 envelope is due to a subsequent growth over the primine, as occurs in other numerous 

 well-known cases. I would not, however, now presume to question the validity of an 

 inference standing upon such high authority as that of my valued friend, without being 

 able to offer reasons grounded upon observations made by me many years ago in Brazil, 

 upon living seeds of Talauma, a genus closely allied to Magnolia. 1st. I found the thick 

 outer tunic to consist of a fleshy or oily matter in distinct granules enclosed within a thin 

 external epidermis, and an inner one of a similar nature; this is the usual texture of 

 arillus, not of testa. 2nd. The coating called tegmen by Dr. Gray, and considered by him 

 as the innermost integument, is in reality the intermediate envelope in Talauma ; it is 

 black in the living state, with a small basal hilum ; a longitudinal furrow runs along its 

 ventral face for the reception of the raphe, and a brown fungous scar, through which the 

 raphe finds a passage to the interior, fills a hollow cup in the apex, where there exists a 

 distinct aperture (the diapyle) for this purpose : this process Dr. Gray, following the 

 example of Endlicher, considers to be the chalaza : the crustaceous envelope is thick and 

 osseous in texture, bearing all the characters of a testa, and certainly none of those of an 

 innermost integument of the seed. 3rd. The existence of a membranaceous inner integu- 

 ment around the albumen, first indicated by Gsertner, within the true testa, thickened 

 and discoloured around its summit by a well-marked chalaza, where it is attached by a 

 short neck to the fungous process that covers the diapyle, and where it unites with the 



* St. Hilaire has expressed similar views in regard to Euphorbiacece (Lecons de Bot. p. 728), founding his notion 

 upon the authority of Schleiden, who, although a very acute observer and a physiological botanist of the highest 

 repute, is not always free from error in his conclusions, and who asserts that the external fleshy coating of the seed of 

 Euphorbia is derived from the primine. I have examined a great many seeds of arborescent Euphorbiacece in Brazil, 

 and have found them generally covered with a coloured fleshy arillus, having a distinct raphe extending from the 

 apical hilum to the basal diapyle of the bony testa, and which cord constantly occurs between the testa and arillus : 

 there always exists a more internal membranaceous integument with its basal chalaza. It is therefore clear in these 

 cases, as in the instances alluded to in the text, that the nourishing vessels proceeding from the placenta through the 

 funiculus to the foot of the primine, will, by the reversion of the ovule, necessarily have become extended with it, and 

 produced along its surface ; and it follows that the raphe, thus resulting and afterwards apparent as a free or imbedded 

 cord, will manifest itself always upon the outer face of the testa (the product of the primine), and that whatever 

 coating may posteriorly appear covering the raphe, such must be of subsequent and exterior growth, and therefore 

 an arillus. 



2l2 



