^" ai 



CONIFERJE. 



507 



ation, which is apparently brought about by insects, the carpels separate from one 

 another, and the micropyle excretes a fluid to which the pollen-grains adhere. The 

 outer layer of the testa is usually fleshy, the inner one hard, and the seed therefore 

 resembles a plum, with its surface often brightly coloured. 



B. CONIFER^i. 



Germination. The endosperm surrounds the embryo in the form of a thick- 

 walled sac open at the radicular end ; the embryo lies straight in the central cavity of 

 the endosperm ; its axis is continuous behind with the rudiment of the primary root, 

 and bears at its anterior end a whorl of two or more cotyledonary leaves, between 

 which it terminates in a roundish apex (Fig. 346 /). The Taxineae and most 

 Cupressineae and Araucariese have two opposite cotyledons, although in some 

 Cupressineae there are from three to nine, and in some Araucarieae whorls of four 

 cotyledons ; while among the Abietineae there are rarely so few as two, more often 

 four or even as many as fifteen. To refer this larger number of cotyledons to the 

 division of two opposite ones, as Duchartre proposes, is entirely opposed to the other 

 processes of leaf-formation in these plants, especially to the common occurrence of 

 whorls consisting of several leaves on the growing axis of seedlings. 



When placed in damp soil the endosperm swells up, bursts the testa at the 

 radicular end of the embryo, which is then pushed out by the elongation of the axis, 

 and grows into a strong descending tap-root, from which lateral roots proceed, suc- 

 ceeding one another rapidly in acropetal succession, and subsequently branching. 

 This is the commencement of the root-system of Conifers, which is frequently 

 strongly developed and persistent. After the emergence of the root, the coty- 

 ledons elongate in their turn, push out their bases from the seed and the end of 

 the axis that lies between them, but they themselves remain in the endosperm until 

 it has been absorbed. In Araucaria (sub-genus Colymbea) and in Salisburia the 

 hypocotyledonary portion of the axis remains short, and the cotyledons remain 



' For the structure of the flowers, see R. Brown, On the Plurality and Development of the 

 Embryos in the Seeds of Coniferae : Misc. Bot. Works, London, 1866, vol. I. pp. 567-576. — H. von 

 Mohl, Vermischt. Schrift. pp. 25 and 49. — Schacht, Lehrb. der Anat. u. Phys. vol. II. p. 433. — Eichler 

 in Flora, 1863, p. 530, [and Nat. Hist. Rev. 1864, pp. 270-290; Flora, 1873, and Trans. Bot. Soc. 

 Edin. 1873, pp. 535-541. — Dickson, Trans. Bot. Soc. Edin. VI. p. 420; New Phil. Journ. 1861, pp. 198, 

 199. — J. D. Hooker, On the Ovary oi Siphonodon in Trans. Liim. Soc. XXII. pp. 137, 138. — Caspary 

 in Ann. des Sci. Nat. 4th series, vol. XIV. p. 200, and Flora, 1862, p. 377. — Brongniart, Bull. Bot, Soc. 

 France, XVIII. p. 141. — Van Tieghem, Ann. des Sci. Nat. 5th series, vol, X.] For the fertilisation, 

 Hofmeister in Vtrgl. Unters.-i85i [On the Germination, Development, and Fructification of the 

 Higher Cryptogams, Ray Soc, pp. 400-433.] — Strasburger, Die Befruchtung der Coniferen, Jena 

 1869. For the pollen, Schacht in Jahr. f. wiss. Bot, vol, II. p. 142, — Strasburger, Ueber die Bestau- 

 bung der Gymnospermen, Jenaische Zeitschr. vol. VI. Also in addition : [Zuccarini, Morphology of 

 the Coniferoe, Ray Soc, Rep, and Pap, on Bot, 1845,] — Pfitzer, Ueber den Embryo der Coniferen, 

 Niederrhein. Ges, fiir Natur. u. Heilk. Aug. 7, 1871. -Reinke, Ueber das Spitzenwachsthum der 

 Gymnosperm-Wurzeln, Gottinger Nachr. 187 1, p. 530. — [Strasburger, Die Coniferen u, die Gnetaceen ; 

 eine morphologische Studie, Jena 1872. — Eichler, Sind die Coniferen gymnosperm oder nicht? Flora 

 1873, and Bluihendiagramme, I. 1875. — Strasburger, Die Angiospermen und die Gymnospermen, 

 1879,] 



