45 2 Scott and Hill.—•Structure of Isoetes Hystrix. 
Mohl, H. VON, 1845 : Ueber den Bau des Stammes von Isoetes lacustris. 
Vermischte Schriften, p. 122. First published in Linnaea for 1840. 
Motelay, L., et Vendryes, 1882 : Monographie des Isoeteae. Actes de la Soc. 
Linn, de Bordeaux, vol. xxxvi. 
NXgeli, C., u. Leitgeb, H., 1868 : Entstehung u. Wachsthum der Wurzeln. 
Beitrage zur wiss. Botanik, Heft IV. 
Russow, E., 1872 : Vergleichende Untersuchnngen . . . Leitbiindel-Kryptogamen. 
St. Petersburg. 
Scott, D. H., 1900 : Studies in Fossil Botany. London. 
Smith, Wilson R., 1900 : Structure and Development of the Sporophylls and 
Sporangia of Isoetes. Botanical Gazette, vol. xxix. 
Solms-Laubach, Graf H. zu, 1899 : Ueber das Genus Pleuromeia. Botanische 
Zeitung, vol. lvii. 
Strasburger, E., 1891 : Histologische Beitrage, vol. iii. 
Van Tieghem, Ph., 1871 : Recherches sur la Symetrie de Structure des Plantes 
Vasculaires. Ann. des Sci. Nat. (Bot.), Ser. 5, vol. xiii. 
■- Traite de Botanique. Second edition, 1891. 
-- et Douliot, H., 1888 : Recherches comp, sur l’origine des 
membres endogenes. Ann. des Sci. Nat. (Bot.), Ser. 7, vol. viii. 
Vines, S. H., 1888 : The Systematic Position of Isoetes . Ann. of Bot., vol. ii, 
pp. 117 and 223. 
EXPLANATION OF FIGURES IN PLATES 
XXIII AND XXIV. 
Illustrating Messrs. Scott and Hill’s paper on Isoetes Hystrix. 
PLATE XXIII. 
Fig. 1. Apical meristem of stem, in superficial transverse section, a, two large 
central cells, of which one may be the apical cell and the other its segment, 
x 576. 
Fig. 2. Part of a similar section from another apex, a, apparent apical cell, 
x 610. 
Fig. 3. Apical meristem of stem in median longitudinal section, a, apparent 
apical cell, x 550. 
Fig. 4. Adjacent section to the last, s, segment-cells, x 550. 
Fig. 5. Transverse section of the upper part of the stele, from a young stem. 
x, primary wood ; l.t , leaf-trace; cb, cambium. The enucleate cells between 
cambium and wood belong largely to the phloem, x 207. 
Fig. 6. Transverse section of the wood of the stele, cut near the apex, x, xylem- 
elements; the differentiation has not yet reached the centre. From a larger stem 
than Fig. 5. x about 200. 
Fig. 7. Peripheral tissues of the stele, in transverse section, x, part of primary 
