This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Handsome erect, diffuse, or climbing perennials with much-divided leaves. Flowers in racemes, terminal, or opposite the leaves. Sepals 2, minute. Petals 4, the exterior oblong, concave, saccate or calcarate at the base, and spreading at the top; the interior clawed, cohering at the tips, and keeled or winged at the back. Stamens 6, in two bundles opposite the outer petals, the filament of the middle stamen of each bundle spurred at the base or naked. Anthers of the middle stamens 2-celled, of the lateral 1-celled. Ovary 1-celled, with 2 placentas and many ovules. There are about a dozen species, natives of North America and North-western Asia. The name is from the Greek two, and a sheath, from the beautiful outer petals.
1. D. spectabilis (fig. 31). - This magnificent hardy plant is now so familiar that details are unnecessary. Its elegant ternately divided foliage and gracefully drooping racemes of locket-like flowers of white and rose are not surpassed by any known plant. It is a native of Siberia, but was introduced by Mr. Fortune from Chinese gardens.
Fig. 31. Dielytra spectabilis. (1/8. nat. size.)
2. D. eximia (fig. 32).- A smaller plant than the preceding, but also very handsome. The habit, it will be seen, is quite different. It grows about a foot high, and bears rosy pink flowers in Summer. A native of North America. D.formosa scarcely differs from this species.
Fig. 32. Dielytra eximia. (1/4 nat. size.)