382 SYSTEMATIC BOTANY. 



Affinities, &c. Among the Bromeliaceae are found "both epigynous and 

 hypogynous genera, as well as forms with a partially adherent perianth ; 

 on the whole, the tendency is to the former condition, whence the Order 

 must be regarded as an ally of Amaryllidacete, from which it differs in 

 habit and in the mealy perisperm ; from Iridaceae it differs in these parti- 

 culars and in the 6-androus stamens, while the style and stigma are 

 somewhat similar. The character of the habit, and the often distinctly 

 characterized calyx and corolla, offer a resemblance to Hydrocharidacese, 

 which, however, have aperispermic seeds. The fruit varies much in this 

 Order, being commonly capsular ; but in Ananassa the entire spike of 

 inflorescence, together with the stem, becomes blended into a succulent 

 sorosis, forming the fruit of the well-known Pine-apple. The scurfy epi- 

 dermis of the leaves displays a very interesting microscopic structure. 



Distribution A considerable group, the members of which are, for the 

 most part, natives of tropical America ; but some are now naturalized in 

 West Africa and the East Indies. 



Qualities and Uses. Chiefly important for the fruit of Ananassa, fibres, 

 colouring-matters, and other economic products. JBromelia Pinguin is 

 used as a vermifuge in the West Indies. Many of these plants grow 

 upon the branches of trees (epiphytic), and they appear to be capable of 

 obtaining the greater part of their nourishment from the atmosphere ; 

 their rigid, tough epidermis enables their succulent leaves to withstand 

 the influence of a hot and dry atmosphere. Tillandsia usneoides, called 

 Old-Man's Beard, is a common plant, forming a dense mass of dark-co- 

 loured fibres, which hang down from the boughs of the trees of the forests 

 of tropical America, as Lichens do in colder climates. Most of the 

 genera have brilliantly coloured flowers, sometimes in tall racemes and 

 panicles, whence they are much esteemed as ornamental stove-plants. 



HYDROCHABJDACE.ZE are aquatic herbs, with diclinous or polyga- 

 mous regular flowers issuing from a spathe on the end of scape-like pe- 

 duncles ; floral envelopes in a single or double circle, in the fertile flowers 

 united into a tube and inseparate from the 1-9-celled ovary; placenta 

 parietal ; seeds without perisperm. Illustrative Genera : Udora, Nutt. ; 

 Vallisneria, Mich. ; Stratiotes, L. ; Hydrocharis, L. 



Affinities, &c. The sum or combination of the characters of this interest- 

 ing Order keeps it apart from all other Monocotyledons, while the characters 

 taken separately connect it with many. The inferior ovary and, in the case 

 of Stratiotes, the habit connect them with Bromeliaceas ; the 3-merous 

 petaloid flower and aperispermic seeds with Alismacese ; the 3-merous 

 petaloid flower and 3-carpellary ovary with the Oommelynaceae, which, 

 however, with a superior ovary, like the Alismacese, have perispermic 

 seeds. The inferior ovary, numerous seeds, and general characters remove 

 them from Naiadacese, with which they are often associated by habit, and 

 the Aracese, with which some would connect them ; their spathe is scarcely 

 more Araceous than that of AmaryUidaceae. Vallisneria and Elodea 

 (Anacharis) are plants well known "to microscopists for the favourable 

 opportunities they offer of examining the rotation of the protoplasm of 

 the cells. Hydrocharis, a plant somewhat like a miniature Water-lily, is 

 common in fresh-water ditches ; and its sepals and rootlets are equally 



