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genera, as Glyceria and Melica. In certain other genera, as Bambusa and 

 Stipa, a third squaraula exists, which is placed opposite to the axis of the 

 upper valve of the proper envelope, or, to speak in conformity with the view 

 already taken of the structure of this valve, opposite to the junction of its 

 two component parts. With these squamaj the stamina in triandrous 

 Grasses alternate, and they are consequently opposite to the parts of the 

 proper envelope ; that is, one stamen is opposed to the axis of its lower or 

 outer valve, and the two others are placed opposite to the two nerves of the 

 upper valve. Hence, if the inner envelope be considered as consisting of 

 bractese, and the hypogynous squamse as forming the perianthium, it seems 

 to follow, from the relation these parts have to the axis of inflorescence, that 

 the outer series of this perianthium is wanting, while its corresponding stamina 

 exist, and that the whole or part of the inner series is produced while its cor- 

 responding stamina are generally wanting. This may, no doubt, actually be 

 the case ; but as it would be, at least, contrary to every analogy in Monoco- 

 tyledonous plants, it becomes in a certain degree probable that the inner or 

 proper envelope of Grasses, the calyx of Jussieu, notwithstanding the ob- 

 liquity in the insertion of its valves, forms in reality the outer series of the 

 true perianthium, whose inner series consists of the minute scales, never 

 more than three in number, and in which an irregularity in some degree 

 analogous to that of the outer series generally exists. It is necessary to be 

 aware of the tendency to suppression existing, as it were, in opposite direc- 

 tions in the two floral envelopes of Grasses, to comprehend the real struc- 

 ture of many irregular genera of the order, and also to understand the limits 

 of the two great tribes into which I have proposed to subdivide it. One of 

 these tribes, which may be called Paniceae, comprehends Ischsemum, Holcus, 

 Andropogon, Anthistiria, Saccharum, Cenchrus, Isachne,Panicum, Paspa- 

 lum, Reimaria, Anthenantia, Monachne, Lappago, and several other nearly 

 related genera; and its essential character consists in having always a locusta 

 of two flowers, of which the lower or outer is uniformly imperfect, being 

 either male or neuter, and then not unfrequently reduced to a single valve. 

 Ischsemum and Isachne are examples of this tribe in its most perfect form, 

 from which Anthenantia, Paspalum, and Reimaria, most remarkably deviate, 

 in consequence of the suppression of certain parts : thus Anthenantia (which 

 is not correctly described by Palisot de Beauvois) diff'ers from those species 

 of Panicum that have the lower flower neuter and bivalvular, in being 

 deprived of the outer valve of its gluma ; Paspalum differs from Anthenantia 

 in the want of the inner valve of its neuter flower, and from those species of 

 Panicum whose outer flower is univalvular, in the want of the outer valve of 

 its gluma ; and Reimaria differs from Paspalum in being entirely deprived of 

 its gluma. That this is the real structure of these genera may be proved by 

 a series of species connecting them with each other, and Panicum with 

 Paspalum. The second tribe, which may be called Poaceae, is more nume- 

 rous than Paniceee, and comprehends the greater part of the European 

 genera, as well as certain less extensive genera peculiar to the equinoctial 

 countries; it extends also to the highest latitudes in which Phainogamous 

 plants have been found ; but its maximum ap[)ears to be in the temperate 

 climates, considerably beyond the tropics. The locusta in this tribe may con- 

 sist of I, 2, or of many flowers; and the 2-flowered genera are distinguished 

 from Paniceae by the outer or lower flower being always perfect, the tendency 

 to imperfection in the locusta existing in opposite directions in the two tribes. 

 In conformity with this tendency in Poaceae, the outer valve of the perian- 

 thium in the single-flowered genera is placed within that of the gluma, and 

 in the many-flowered locusta the iqiper flowers are frequently imperfect. 

 There are, however, some exceptions to this order of suppression, especially 



