TERMINOLOGY IN MONOCOTYLEDONS. 497 



distinct orders, which have been very variously placed by different 



botanists. 



Philydracese, limited to four Australian or East -Asiatic species 

 distributed in three genera, cannot nevertheless be brought into, 

 or even very near, any other order. The general structure of the 

 ovary and some other points induced me in the ' Flora Hongkong- 

 ensis,' to refer them to Xyridese ; but the anatropous ovules and 

 basal embryo are rather those of Liliacea;, whilst the peculiar 

 irregularity of the flowers with only one perfect stamen and two 

 staminodia is that of Scitamineae ; and the perianth is quite ab- 

 normal, consisting of two rather large petals only ; the upper 

 two-nerved one, however, is apparently formed by the combina- 

 tion of two; and the perianth must be probably regarded as limited 

 to the inner series, the outer series being entirely deficient. 



Xyridese, on account of their glumaceous inflorescence and 

 orthotropous ovules, have been, by Martius and others, associated 

 with Restiaceaj and some others in a separate alliance. Xyns, 

 however, differs essentially from the latter order, as well in the 

 great petaloid development of the inner perianth, as in the struc- 

 ture of the ovary. The imbricate glume-like bracts each embra- 

 cing a single sessile flower occur also in Johnsonia and its 

 allies among true Liliacea? ; and the structure of the seed, although 

 usually one of the most important characters, may, like all others, 

 become purely artificial if unaccompanied by other differences. 



I would here observe that there is one point in which the ho- 

 mology of the parts of the flower in Xyris appears to me to have 

 been in some measure mistaken. The two outer scales ( Plate VII. 

 figs. 1-3), usually regarded as two outer perianth-segments, are 

 placed opposite to each other at the very base of the floral axis ; 

 they are concave or complicate, and keeled, and persist after the 

 true perianth has fallen away or shrivelled up ; they have there- 

 fore all the characters of the bracteoles observable in many genera 

 of the epigynous as well as of the coronal orders. The next, or 

 so-called third 'perianth-segment of the outer series is placed 

 higher up on the floral axis, immediately under the inner series 

 with an annular attachment perfectly closed round the axis when 

 in bud ; it is of a very different texture from the bracteoles, 

 completely encloses the inner segments in the young bud, disar- 

 ticulates at the base, and is cast off as those inner segments 

 grow out. This so-called third segment would therefore appear 

 rather to represent the whole outer series, and to consist of the 



LTNN. JOUBN. — BOTANT, VOL. XV. Z V 



