. Bulletin. Science; Natural history; Natural history. NOTES ON DELESSERIACEAE 165. Figs. 1 and 2. Fig. 1. Hypoglossum gregarium. Camera lucida drawing of apex of holotype. Sym- bols: 2, cell of 2nd-order row; 3, cell of 3rd-order row; 4, cell of 4th-order row; /, cell derived from an intercalary division. Fig. 2. Membranoptera spatulata. Camera lucida drawing of apex of holotype. is represented in Fig. 1. Stewart correctly recognized that Dawson's species cannot be placed in Hypoglossum because not all tertiary initials reach the thallus margin and cells of second-order rows undergo intercala
. Bulletin. Science; Natural history; Natural history. NOTES ON DELESSERIACEAE 165. Figs. 1 and 2. Fig. 1. Hypoglossum gregarium. Camera lucida drawing of apex of holotype. Sym- bols: 2, cell of 2nd-order row; 3, cell of 3rd-order row; 4, cell of 4th-order row; /, cell derived from an intercalary division. Fig. 2. Membranoptera spatulata. Camera lucida drawing of apex of holotype. is represented in Fig. 1. Stewart correctly recognized that Dawson's species cannot be placed in Hypoglossum because not all tertiary initials reach the thallus margin and cells of second-order rows undergo intercalary divisions. Stewart thus estab- lished Phrix, distinguishing it from such genera as Delesseria, Grinnellia, and Apoglossum by the absence of transverse divisions by the lateral pericentral cells in Phrix. Additional criteria of her new genus included a conspicuous but un- thickened midrib and the vague or indistinct nature of the lateral veins. Although it is true that the lateral pericentral cells in Delesseria and Grinnellia undergo transverse divisions, the lateral pericentral cells of Apoglossum ruscifo- lium (Turn.) J. Ag., the type of the genus, have been clearly depicted as not undergoing such transverse divisions (Kylin 1923, 1956; Coppejans 1983; Wynne 1984). The development of the midrib in A. ruscifolium is initiated by the cutting off of small cells from the comers of the transverse and lateral pericentral cells (Coppejans 1983, p. 227, fig. 2). These small cells then grow downward, elongating, dividing, and investing the underlying primary cell layer. The lateral pericentral cells, although covered with this rhizoidal cortication, remain undivided trans- versely (Kylin 1923, fig. 55; Wynne 1984, fig. 28). This difference is a useful feature to distinguish Apoglossum from the related genera Delesseria and Gn«- nellia (Wynne 1983). Since Phrix gregarium cannot be separated from Apoglossum in regard to the behavior of the lateral pericentral cells, one next conside
Size: 2089px × 1196px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectnaturalhistory, booksubjectscience
