LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
595 
that he thought that at least in Zamia muricata the development of the whole leaf, 
and its extension proceeded from base to apex. In the former of the two passages 
however he describes the first appearance of the pinnae as “ semi-lunar weals ”; this 
does not correspond to my own observations on other Cycads. Thus there are two 
questions to be decided : first, in what form do the pinnae first appear ? second, do 
they ajjpear in acropetal or in basipetal succession ? 
On examining young leaves of Zamia muricata it was found that the form of the 
pinnae on first appearance, and their order of succession, were similar in all essential 
points to that described in Macrozamia and Ceratozamia. Thus the pinnae do not 
arise as “ half-moon-shaped weals ” but as undulations of the surface of the ridges, 
which round themselves off as hemispherical papillae, and then subsequently assume 
the obliquely ellipsoidal form. Further, the order of succession of their appearance is 
clearly basipetal, and no signs of any acropetal succession were found in the leaves 
investigated. Judging from Karsten’s description of the first appearance of the 
pinnae as “ semi-lunar weals,” I should think that he did not see the earliest stages of 
their development at all, though such observations alone can give true ground for 
statements as to the order of development of the parts of the leaf. 
Marginal crenations or teeth are found on the pinnae of most if not all species of 
Zamia, and some observations were made upon their origin, and the time of their 
appearance. They are absent from the basal part of the pinnae; the margin of the 
apical part of the pinna is seen at an early stage to be crenated [Z. Bolivian a f 
= Loddegesii), even while the lignificat ion of the vascular bundles has hardly begun : as 
to the order of development of the crenations, I have not been able to come to any 
conclusion, but it may readily be seen in young pinnae that they are more marked at 
the lateral margins than at the apex. Each crenation corresponds in position to the 
end of one of the procambial strands, or vascular bundles : this may be compared with 
what has already been observed by Prantl* in the leaves of certain Ferns, in which, 
as he describes it, the ends of some of the nerves (hence called ribs, costa) perform 
the function of growing points during the development of the leaf: a similar but very 
rudimentary development is to be found in most of the Encephalartece,, also in Botry- 
chium, and in Ginkgo. 
The phyllopodium of Zamia ends in a terminal spine. During the extension and 
unfolding of the leaf there is a curvature of the phyllopodium, which has been 
regarded as bearing an outward resemblance to leaves with circinate vernation. This 
curvature, however, appears only at a comparatively late period, the phyllopodium of 
young leaves being straight in those plants both of Zamia and of Ceratozamia, which 
I have observed. 
* Untersucbungen zur Morpliologie der Geflisskryptogamen. Heft I., p. 4, Ac., Heft II., p. 4, Ac. 
4 Cx 2 
