FEBRUARY. 39 



of which have reticulated veins. Such of these genera as exist in 

 gardens will be more fully described when we come to treat of the 

 species in cultivation. 



The Platyceriece consist of three genera, of which the first and 

 typical one has generally been associated with the Acrostichece. It is, 

 however, materially different, and we have proposed to separate it. 

 The other genera have, in their aspect and general habit, some affinity 

 the former of them with the Polypodiece and the latter with the 

 Acrostichece, but they are brought here on account of the compound 



§2. Platycerie.£ : Platycerium Stemmaria. 



condition of their receptacles. The three genera are separated by 

 their sori, which in Platycerium are few, very large, and amorphous 

 or shapeless — that is, of no definite or constant form ; in Dryostachyum 

 much smaller and more numerous, and quadrate in outline ; and in Jen- 

 kinsia forming linear submarginal patches along each side of the costa. 

 We may sum up the foregoing in a brief contrasted form, thus : — 



a]. Receptacles universal . . . . . . §1. Acrostichece. 



b]. Receptacles compound effuse crowded indefinite . |2. Platyceriece. 



c]. Receptacles local determinate definite [see forward) . 



The remaining larger portion of the Polypodinece, in which the 

 receptacle is local, circumscribed, confined to determinate parts of the 

 veins, and of definite form, have still to be subdivided. The most 

 convenient characters for this purpose seem to be those derived from 

 the form and position of the sorus in relation to the vein on which it 

 is placed. There is of course a considerable amount of variety in 

 respect to the form and position of the sori to be observed among the 

 plants which we have now under consideration, but they may with 

 tolerable exactitude be reduced under three heads. These it will be 

 convenient to state in a distinct and brief form, so as to admit of ready 

 comparison, and the actual structure intended should be well under- 

 stood, which it may be by the careful study of a few common species as 

 illustrations. We have then — 



Receptacles local determinate definite — 



(1). Sori transverse to the veins, parallel or sub-parallel with the costa or 

 margin, usually elongated. 



(2). Sori parallel with the veins, oblique to the costa, more or less elongated, 

 sometimes reticulated. 



(3). Sori punctiform, rarely suboblong, or by confluence elongated. 



