64 CELLULAR TISSUE. 



E), Platycerium, and from capitate hairs. The families Oleaceae and Jasminese ' yield an 

 especially complete series of forms, from the 8-celIed shield, produced by triple radial 

 division of the initial cell (Syringa), or a i6-ccllcd shield (Fraxinus), to the 30-32-celled 

 star (Olca Euiopxa). Further examples of the forms of this category are the above- 

 named Elaeagneae, single species of Solanum (S. argenteum, Dun., and allied ' lepidota'), 

 Croton (Cr, pseudo-china, nitens), Capparis Breynia, Andromeda calyculata, Myrica 

 cerifera-. Further the leaves and stem of Callitriche and Hippuris^, and the long- 

 stalked scales on the leaf of Pinguicula*. Large scutiform scales with pluriseriate, 

 multicellular central part, and radial multicellular margin, cover the leaf of most 

 Bromeliacea;, e.g. Hechtia planifolia, stenopetala, Tillandsia usneoides'', Pholidophyllum 

 '/onatum, Billbergia clavata, Bromelia bracteata ; the young leaves of many Palms, e. g. 

 Klopstockia cerifera '', with scales several layers of cells thick in the middle. 



As regards their external development, there further belong to this category the 

 circular, shield-shaped, glandular scales of many plants, consisting of few cells (e. g. 

 Thymus, Sahia), or of many arranged in several series (Rhododendron ferrugineum, 

 Humulus lupulus, Ribes nigrum, &c.). The peculiarities of their structure will be 

 treated of later (Sect. 19). 



Of scales attached at one side the Ferns yield the richest and best known examples, in 

 their so-called chaff-scales, or Palex. Among these occur various intermediate forms 

 between purely single-layered hairs, such as are many-layered at their insertion, uni- and 

 multiseriate hairs, and shag-hairs. Their relations of size, form, and structure, so often 

 made use of for descriptive purposes, may with a reference to the descriptive literature 

 be here left untouched ". Those large branched scales on the stem of Hemitelia capensis, 

 the similarity of which to leaves of the Hymenophyllums caused them to be described as a 

 species of Hymenophyllum, are not to be included under epidermal structures, since 

 they have vascular bundles, and an epidermis with stomata^ Uhlworm mentions in the 

 case of Alsophila aspera thorn-emergences, which bear on their apex a large scale. 



In the Phanerogams examples of this category may be sought among those forms 

 which form shag-hairs, inasmuch as these bodies are often developed chiefly in the direc- 

 tion of one transverse diameter, i.e. into many-layered elongated scales. This is the 

 case on the leaf-endings and margins of species of Papaver, in the INIelastomeae, as species 

 of Lasiandra, Melastoma malabathricum ", &c. To this category belong also the dermal 

 scales, borne on scale-like emergences, of Begonia manicata and its allies. As a special 

 very simple form allied to stellate, tufted, or capitate hairs, may finally be mentioned the 

 scales occurring in the axils of the leaves of Hippuris and Callitriche (Hegelmaier, I.e., 

 Rauter, /. c). These are borne on a short simple stalk-cell, and appear as a circular fan 

 one layer of cells thick, which is composed of radially arranged elongated cells, or 

 (Pseudo-callitriche) of rows of cells similarly arranged. 



III. On bhag-hairs (Zotten) (Fig. 21, C, a, c) little need here be added to what 



' Prillieux, De la structure des polls des Oleacees et des Jasminees, Ann. Sci. Nat. 4 Ser. V. 

 p. I, pi. 2-3. 



* Rudolphi, /.c. p. 114, where generally are very numerous details, though there is occasionally 

 a confusion with tufted hairs. 



' Hegelmaier, Monogr. d. Gait. Callitriche. p. 11 ; Rauter, /. r. p. 6. 



* Schacht, Pflanzenzelle, Taf. VII. p. 16.— Lehrbuch, I. p. 2S0. — Gronlaiid, Ann. Sci. Nat. 

 4 .Ser. III. p. 297, Taf. X. 



' Compare Schacht, Lehrb. I. Taf. IV. pp. 10, 11 ; Pflanzenzelle, Taf. VII. pp. 17, 18. 



^ How far the scaly or fibrous covering of the unfolding palm leaves consists of hair structures, 

 or of effete drying masses of tissue, requires more complete investigation in special cases. Compare 

 Mohl, Verm. Schr. p. 177, Structura palmarum, § 82. 



'^ On their development, compare Hofmeister, Vergl. Unters. p. 85. 



" Compare Mettenius, Filiccs horli Lipsiensis, p. iii. 



* Rudolphi, I.e. p. 115. 



