27 



Triuris, which the author originally suggested would form the type of 

 a distinct order (Triuriaceae), subsequently adopted by Dr. Gardner, 

 under the name of Triuraceae. He first dismisses without hesitation 

 the hypothesis that they have any relationship to Menisperraaceae or 

 Smilaceae, as suggested by Dr. Gardner with reference to Hexuris ; 

 or to any section of Urticeae, to which Sciaphila was referred by Dr. 

 Blurae, and in which he was followed by Endlicher and Gardner. 

 He commences his investigation by calling particular attention to 

 their habitat as plants destitute of real leaves; composed of little more 

 than cellular tissue ; void of green colour, of fibres and of ducts; and 

 furnished with a seed not merely acotyledonous, but without distinct 

 embryo. He refers to Mr. Brown's memoirs on RafHesia, and to Mr. 

 Griffith's on the plants referred to Hhizantheee, for instances of inem- 

 bryonal seeds ; and observes that we have no satisfactory evidence of 

 the existence of an embryo, in the ordinary sense of the term, in 

 Burmanniaceae. He notices also the imperfect condition of the 

 embryo in Cuscuta, in Orobancheae and in Monotropa ; and the 

 striking discrepancy between the well-developed cotyledonous embryo 

 of the leaf-bearing Cacteae and the solid and undivided embryo of the 

 leafless genera of that family. Admitting then, in Triuriaceae, Bur- 

 manniaceae, Belanophoreae, &c., the existence of an organ endowed 

 with the function, but wanting the usual structure, of the embryo, he 

 proposes for this organ the name of protohlastus, with the view of 

 distinguishing between aprofoblasteous and a cotyledouous embryo. 

 Modifications of the protoblasteous structure may occur ; and the 

 author refers to Ceratophyllura and to several genera of Aroideae 

 (especially Cryptocoryne) as furnishing instances of anomalous forms 

 of embryo, which are best explained by a reference to this view of 

 the subject. He also notices some peculiarities in the structure of 

 the seed of Pistia, which he regards as in some points analogous to 

 that of Sciaphila, although widely different from it in others. 



Setting aside then the acotyledonous embryo as a character of 

 primary importance, and regarding it only as an imperfect condition 

 of development, common to all the great divisions of the vegetable 

 kingdom, it is evidently among the Endogens that Triuriaceic should 

 take their place, and the author concludes that upon the whole tlic 

 greatest amount of appi'oximate characters leans towards Fluviales. 



