GYMNOSPERMA E. CYC A DEA E. 313 



A. CYCADEAE J . 



The Cycadeae form the group of Gymnosperms which comes nearest in habit 

 and in other respects to the Vascular Cryptogams and especially to the Ferns, and 

 among the Ferns they show the greatest affinity to the Marattiaceae ; like them they 

 played an important part in former epochs of the world's history, and with the 

 Coniferae were once the chief representatives of the Phanerogams. 



Leaves. The whole surface of the stem is covered with large leaves arranged 

 spirally, and no internodes can be distinguished. At the summit is a crown of leaves 

 more or fewer in number, as in many Ferns. The leaves are of two kinds ; large, 

 stalked, pinnate or pinnatifid foliage-leaves alternate periodically with dry, sessile, 

 leathery scale-leaves, covered with brown hairs and of comparatively small size, which 

 usually much exceed the foliage-leaves in number within the several periods. This 

 alternation of scale-leaves and foliage-leaves, which is not uncommon in the Coniferae 

 and in Angiosperms, is found in the Ferns only in the genus Osmnnda 2 '. The scale- 

 leaves are in this case, as in most others 3 , transformed rudiments of foliage-leaves, in 

 which the broad part of the leaf has been arrested in its growth, while the base has 

 attained to considerable development. Every year or every second year a rosette 

 of large foliage-leaves is formed, and among them is the terminal bud of the stem 

 enveloped in scales, under the protection of which the new crown of foliage -leaves 

 slowly developes. This alternation begins in Cycas and other genera at the time of 

 germination, since the cotyledons which are like the foliage-leaves are followed by a 

 number of scale-leaves which envelope the bud ; the bud produces as a rule only a 

 pinnate though as yet small foliage-leaf, and this is followed by scale-leaves. In Zamia 

 on the contrary the formation of scale-leaves precedes that of foliage-leaves. In both 

 cases as the plant grows stronger, foliage-leaves are being constantly produced in 

 greater size and numbers, to form, when the older leaves have died off, the crown of 

 leaves of the time being, while the scale-leaves which stand above enclose at the same 

 time the bud of the stem. The basal portions of the older leaves together with old 

 scale-leaves form a peculiar kind of scale-armour on the stems of some species of Cycas, 

 Encephalartos, Cera/ozatm'a, and other genera. The foliage-leaves are so fully formed 

 within the bud, that when they burst it they have only to unfold, and this takes 

 but a short time, while one to two years elapse before the next rosette unfolds. The 

 arrangement of the leaves in the bud also recalls to some extent that of the Ferns ; 

 the pinnae of Cycas are circinate, the leaf as a whole is stretched straight out ; in Zamia 

 and Ceratozamia the leaf in general with its apex is more or less bent or loosely rolled 



1 Miquel, Monographia Cycadearnm, 1842. Karsten, Organographische Betracht. ti. Zamia 

 i/iiii-icata, Berlin, 1857. Mohl, Bau d. Cycadeenstammes (Verm. Schr. p. 195). Mettenius, Beitr. z. 

 Anat. d. Cycadeen (Abhandl. d. Kgl. Sachs. Ges. d. Wiss. VII, 1861). De Bary, Vgl. Anat. vid. inf.- 

 Kraus, Ueber d. Bau d. Cycadeenfiedern (Jahrb. f. wiss. Bot. Bd. IV). De Bary in Bot. Ztg. 1870, 

 p. 574. Juranyi, Bau u. Entw. d. Pollens bei Ceratozamia (Jahrb. f. wiss. Bot. Bd. VIII, p. S^ 2 )- 

 Braun, Ueber d. Gymnospermie d. Cycadeen (Mon. Ber. d. Berl. Ak. 1875. Warming, Untersogelser 

 og Betragtninger over Cycaderne (Kon. Danske Videnskabes Selsk. obersigter, 1877) ; Id. Bidrag til 

 Cycadernes Naturhistorie, overs, over d. Kgl. D. Vidensk. Selsk. Forh. 1879. Treub, Recherches 

 sur les Cycadees (Annales. du jardin Bot. de Buitenzorg, II, 1881 [and IV, 1884]). [Goroschankln, 

 Zur Kenntn. d. Corpuscula b. d. Gymnosp. (Bot. Ztg. 1883).] 



~ According to Prantl, but not in all specimens. 



3 Gobel, Beitr. z. Morphol. u.Physiol.d. Blattes (Bot. Ztg. 1880, 11.753). [See note on next page.] 



