ON SECTION AVICULARIA OF THE GENUS POLYGONUM. 663 
tinctive characteristics are the leaf jointed upon the petiole at the 
point of divergence from the sheath ; the broadly dilated filaments 
of the three inner stamens; and the incumbent cotyledons. Of 
these the first occurs in no other section of the genus, excepting 
§ Tephis, of a single species, but is found in Atraphagis, Thysa- 
nella and Polygonella, of the subtribe Rumicee. The second is 
also peculiar to § Tephis, but exists in Atraphazis and a section of 
Polygonella; while the third, occurring besides only in § Ambly- 
gonon of Polygonum, is characteristic of Rumex, Atraphaxis, Thy- 
sanella and some species of Polygonella. The closest affinity of 
the section is to the genus Afraphazis, which has also perfect 
flowers and the same peculiar stipular sheaths, and from which it 
is distinguished mainly by its more or less herbaceous sepals 
not enlarging or deflexed in fruit but appressed to the achenium. 
It would seem that the genus Polygonum should be restricted to 
the two sections Avicularia and Tephis, on account of this, in these 
respects, nearer relationship to the Rumicee than to the other sec- 
tions with which they are at present united. 
The species P. articulatum, which was long retained in § Avicu- 
laria, but referred by Meisner to Polygonella, and restored by Dr. 
Gray to Polygonum as § Pseudo-polygonella, must be placed with 
Polygonella ericoides (which includes P. Meisneriana), having a sim- 
ilarly excentric embryo, somewhat contorted, and the cotyledons 
either accumbent or incumbent. Its scarcely dilating inner sepals 
are those of Polygonella polygama (P. parvifolia), and its colored 
Marcescent calyx, the solitary flowers upon elongated pedicels 
jointed near the middle, and the peculiar floral sheaths, are com- 
mon to all the species of Polygonella in contradistinction to those 
of Po? ygonum 
The sition Avicularia and the North American aes be- 
longing to it may be defined and arranged as follows :— 
§ AVICULARIA, Meisn. Calyx more or less herbaceous, at length connivent upon 
the achenium, 5- or rarely 6- parted; stamens 5-8, som 
Sheaths or rarely solitary, the pedicels jointed to the short base of the calyx; bractlets 
hyaline 
*Smooth perennials (P. tl t 
what woody at base, the slender branches tea to the top; leaves thick; stipules 
Syueptouous; calyx mostly color ed. rather open, exceeding the lanceo- 
ms 8. 
os MEE 
