•208 ORGANOGRAPHY. BOOK I. 



here called secundine is not primine, and the supposed pri- 

 mine ariUus. 



The inner membrane (secundine) of the ovule, however, 

 in general appears to be of greater importance as connected 

 with fecundation, than as affording protection to the nucleus 

 at a more advanced period. For, in many cases before im- 

 pregnation, its perforated apex projects beyond the aperture 

 of the testa, and in some plants puts on the appearance of an 

 obtuse, or even dilated stigma; while in the ripe seed it is 

 often either entirelv obliterated, or exists onlv as a thin film, 

 which might readily be mistaken for the epidermis of a third 

 membrane, then frequently observable. 



" This third coat (tercine) is formed by the proper mem- 

 brane or cuticle of the nucleus, from whose substance in the 

 unimpregnated ovule it is never, I believe, separable, and at 

 that period is very rarely visible. In the ripe seed it is dis- 

 tinguishable from the inner membrane only by its apex, 

 which is never perforated, is generally acute and more deeply 

 coloured, or even sphacelated." 



Mirbel has, however, justly remarked that the primine and 

 the secundine are, in the seed, very frequently confounded; 

 and that, therefore, the word testa is better employed, as one 

 which expresses the outer integument of the seed without 

 reference to its exact origin, which is practically of little im- 

 portance. The tercine is also, no doubt, often absent. He 

 observes that these mixed integuments often give rise to new 

 kinds of tissue ; that in Phaseolus vulgaris the testa consists, 

 indeed, of three distinct layers, but of those the innermost 

 was the primine; and that the others, which represent nothing 

 that pre-existed in the ovule, have a horny consistence, and 

 are formed of cylindrical cellules, which elongate in the 

 direction from the centre to the circumference. And this is 

 probably the structure of the testa of many Leguminosas. 



It sometimes happens that the endopleura (or tercine?) 

 thickens so much as to have the appearance of albumen, as 

 in Cathartocarpus fistula. In such a case it is only to be dis- 

 tinguished from albumen by gradual observation from the 

 ovule to the ripe seed. 



