CrCADE^. 



501 



A. CYCADE^i. 



The Embryo^ enclosed in the large endosperm, possesses two opposite unequal 

 cotyledonary^ leaves, which lie with their inner surfaces face to face, cohering 

 towards their apices. The tendency of 

 the subsequent foliage-leaves to branch is 

 sometimes displayed even in these cotyle- 

 dons, a rudimentary lamina being formed 

 on the larger one, with an indication of 

 pinnae (as in Zamia, Fig. 342 B'). The 

 seed germinates when laid in moist earth, 

 but only after a considerable interval ; the 

 testa splits at the posterior end and allows 

 the emission of the primary root, which 

 at first grows vigorously downwards, but 

 sometimes assumes afterwards a tuberous 

 form or produces a system of rather thick 

 fibrous roots. According to Fig. 342 C 

 borrowed from Schacht, and a more recent 

 statement by Reinke, the branching of the 

 primary root is laterally monopodial; Mi- 

 quel, however, asserts the existence of 

 bifurcations of the more slender roots in 

 older plants of Cycas glauca and Encepha- 

 lartos. According to Reinke and Stras- 

 burger, only those lateral roots which 

 emerge from the ground branch dichoto- 

 mously, probably as a pathological pheno- 

 menon. By the elongation of the coty- 

 ledons which remain in the endosperm 



Fig. 342.— Gerniiuation of Zamia spiralis (after Schacht. 

 reduced). B conimencenient of gerniiuation, ct the cotyledons 

 coherent above their elongated base, one of them having at 

 its apex (magnified at B') an indication of a pinnate lamina ; 

 C seedling six months old ; sa seed, ?£/ tfte primary root, * the 

 first pinnate leaf, Jfx rudiments of the adventitious roots whkh 

 afterwards grow upwards. 



^ Miquel, Monographia Cycadearum, 1842. [Ditto, On the Sexual Organs of the Cycadacese ; 

 Journ. of Bot., March and April 1869]. — Karsten, Organogr. Betracht. iiber Zamia muricata, Berlin 

 1857. — Mohl, Bau des Cycadeenstammes (Vermischt. Schrift. p. 195). — Mettenius, Beitrage zur 

 Anatomic der Cycadeen (Abhandl. der konigl. Sachs. Gesellsch. der Wissensch. vol. VII, 1861). — 

 [W. C. Williamson, Contributions towards the history of Zamia gigas, Trans, l.inn. Soc. vol. XXVI, 

 1870. — Carruthers on Fossil Cycadean Stems from the Secondary Rocks of Britain, ibid.'] — On the 

 structure of the pollen see Schacht, Jahrb. fiir wissensch. Bot. vol. II. p. 142 et seq. — Kraus, Ueber 

 den Bau der Cycadeenfiedern (Jahrb. fiir wissensch. Bot. vol. IV). — Reinke in Nachrichten der konigl. 

 Gesellsch. der Wissensch. in Gottingen, 1871, p. 532.— De Bary, Bot. Zeitg. 1870, p. 574. — Juranyi, 

 Bau u. Entwickelung des Pollens bei Ceratozamia (Jahrb. fiir. wissensch. Bot. vol. VIII. p. 382). — 

 Ueber Wachsthum und Verzweigung der Wurzeln, Reinke, Morphol. Abhandl. 1873. — [Warming, 

 Undersogelser og Betragtninger over Cycaderne, and, Bidrag til Cycadeernes Naturhistorie, in the K. D. 

 Vidensk. Selsk. Forhandl. 1877 and 1879; also Bot. Zeitg. 1878.] 



^ Van Tieghem found in three seedlings, hybrids of Ceratozamia longifolia ? with Cer. Mexicana i, 

 only a single sheathing cotyledon, in another two very unequal cotyledons. Two embryos of Zamia 

 spiralis had two unequal cotyledons, another had three, and another had only one. (See Van Tieghem 

 in the French edition.) 



