CFCADE.E. 



437 



unfrcquently found at the base of the stem under or above ground, the morphological 

 nature of which is still doubtful ; in Miquel's opinion it is not impossible that they 

 spring from old leaf-scales, and have therefore nothing to do with the branching of 

 the stem. 



The whole of the surface of the stem is furnished with leaves arranged 

 spirally; no internodes can be distinguished. The leaves are of two kinds; dry, 

 brown, hairy, sessile, leathery scales of comparatively small size, and large, stalked, 

 pinnate or pinnatifid foliage-leaves. The scales and the foliage-leaves alternate 

 periodically ; a rosette of large foliage- 

 leaves is produced annually or bien- 

 'nially, and among these the terminal 

 bud of the stem is enveloped with 

 scales, under protection of w^hich the 

 new whorl of foliage-leaves is slowly 

 formed. This alternation begins at 

 once on germination in Cycas and 

 other genera, a number of scale-leaves 

 following the leaf-like cotyledons, and 

 enveloping the bud of the seedling ; 

 after these a pinnate though small 

 foliage-leaf is then usually developed, 

 which is again followed by scales. It 

 is only as the strength of the plant 

 increases after several years' growth 

 that the foliage-leaves are produced in 

 whorls constantly increasing in size, 

 and forming, after the older ones have 

 died off, the palm-like crown of 

 leaves, the scales which stand above 

 them enclosing at the same time the 

 apical bud of the stem. In this bud 

 the foliage-leaves are so far formed 

 beforehand, that when they at length 

 burst the bud they only have to un- 

 fold, this process then occupying only a very short time, while one or two years 

 elapse before the unfolding of the next rosette of leaves. The leaves which proceed 

 from the bud are in Cycas and other genera circinate like those of Ferns ; in others 

 the rachis of the leaf only is rolled up; in others, finally, as Dion, the growth of 

 the leaf is straight, its lateral leaflets being also straight before expansion \ The 

 unfolding is, as in Ferns, basifugal, and, probably in consequence of this, there is 

 also a permanent apical growth and a basifugal development of leaflets. The 

 leaflets are usually simple, and generally stand alternately on the rachis, which is 

 often I to 2 metres long. The mode in which the lamina terminates above points 



Fig. 313. — Germination of Zayiiia spiralis (after Scliacht, 

 reduced). B commencement of germination, 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, w the primary root, 

 b the first pinnate leaf, x x rudiments of the adventitious 

 roots which afterwards grow upwards. 



» [This statement is not quite exact. In Zamia and Encephalartos the leaves are not circinate 

 in vernation ; and even in Cycas it is only the leaflets and not the rachis that is so.— Ed.] 



