LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
593 
Encephalartos Barteri. 
This plant affords a most conclusive proof of a development of pinnae exclusively in 
basipetal order. The average number of pinnae on each side of the mature leaf of the 
plant investigated was rather over 40. The apex of the phyllopodium extends beyond 
the topmost pinnae as a short terminal spine : at the margin of the mature pinnae, and 
especially near the apex, a number of spinous outgrowths (pinnules V) are formed. 
The leaf has in its early stages of development a similar conformation to that in the 
forms already described, but the wings at the base of the leaf are of large size, and 
subsequently extend upwards as in Ceratozamia ( cf. infra). No pinnae are formed, at 
least in the plant dissected, till the young leaf has attained a considerable size, with 
well developed ridges running to the apex (Plate 39, fig. 38). The formation of pinnae 
then begins dose to the apex, as a series of rounded papillae, which subsequently 
become ellipsoidal, their longer axes being oblique to the phyllopodium (Plate 39, 
fig. 39). There are no signs of any development of pinnae in acropetal order ; on the 
other hand all evidence tends to show that the order of succession is exclusively 
basipetal. Thus (1), the pinnae decrease in size from above downwards ; (2) as above 
mentioned, the average number of pinnae on each side of the leaf of the plant in ques¬ 
tion was over 40 : in the leaf represented in Plate 39, fig. 39, there are 12 on each 
side, while a considerable space intervenes between the lowest pinnae and the basal 
wings; in the next older leaves this space is occupied by young pinnae. There is 
thus conclusive proof of an exclusively basipetal order of development of the pinnae in 
this plant. Marginal spines, similar to those in Macrozamia Miqueli, are formed at a 
comparatively early period on the pinnae. 
Ceratozamia Mexicana, Prong. 
Observations were made upon a well-grown plant of this species, which had four 
fully-developed foliage-leaves. Each of these bore from 18 to 28 pinnae, that is 9 to 
14 on each side of the phyllopodium. The pinnae near the apex are arranged in 
regular pairs, while those nearer the base are less regular in this respect; and it may 
be here remarked that this is generally, but by no means always, the case with those 
members of this group in which the development proceeds in basipetal order. On 
the other hand, in those plants which like Cycas have divaricating order of develop¬ 
ment, the pairs at the point where development first begins are most regular, while the 
regularity is not so marked in the later formed pinnae. There appears then to be, 
roughly speaking, a tendency to regularity of arrangement in pairs among the pinnae 
first formed, and a gradually increasing irregularity in those formed later. But this 
does not hold without exception. 
The lower part of the phyllopodium, when mature, bears numerous spines 
irregularly arranged. These resemble the spine-like pinnae of C. JenTcinsiana in 
MDCCCLXXX1Y. 4 G 
