LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
579 
in the Osmundacece may therefore be regarded as an advance upon the leaves of other 
Leptosporangiate Ferns ; the phyllopodium is, at least in the part derived from the 
three-sided apical cell, a structure which develops from the first as a solid structure. 
On the other hand, it is of interest to note that though there is this difference 
between the Osmundacece and other Leptosporangiate Ferns, still the conformation of 
the leaf is fundamentally the same. The phyllopodium and pinnae, &c., are essentially 
winged structures to their extreme base. Putting this fact into relation with the 
observations of Kny, on the want of coincidence of origin of the pinnae with the limits 
of the segments cut off from the apical cell in the leaf of Ceratopteris, and with 
Treub’s observations on Selaginella Martensii, it appears that the external conforma¬ 
tion of the member or system of members is to a great extent independent of the 
arrangement of the internal cell-walls. 
Marattiacea:. 
Angiopteris evectci, Hoffm., var . pruinosa, Kuntze. 
For comparison with the Osmundacece on the one hand, and with the Cycadcwece on 
the other, I have had the opportunity of dissecting a well-grown plant of Angiopteris 
evecta, from Java. The amount of material being limited, several points of considerable 
interest have escaped observation, while on other points the evidence is not conclusive. 
This is especially the case with the observations on the apex of the stem. Holle 
remarks (Bot. Zeit., 1876, p. 218) that the reference of the cells of the punctum 
vegetationis to the divisions of a single apical cell is not certain, but he regards it 
as probable that they all originate thus from a single cell. My own observations 
point clearly to the existence of a wedge-shaped apical cell, but I am not in a position 
to state whether the cell has two or three edges, or what is the succession of segments 
cut off from it. Such a cell is represented in Plate 37, fig. 9, and though I will not 
vouch for the accuracy of direction of some of the less important cell-walls there 
drawn, this at least is quite secure, that the apical cell is a conical one, and that the 
tissues of the punctum vegetationis owe their origin to segments cut off from it. The 
question is left open whether this structure, found in a well-grown plant, is constant 
for the species. 
The leaf originates as a flattened swelling of the surface of the very slightly conical 
apex of the stem. The growth is from the first more active on the side further 
removed from the apex of the stem (dorsal). The apex of the leaf is thus curved at 
an early stage towards the apex of the stem. A transverse semi-circular weal arises 
on the ventral side of the young leaf, and at some distance below the apex (Plate 37, 
figs. 10, 11) ; it soon shows signs of greater enlargement in its lateral portions than 
at the centre : this weal is the first origin of the well-known “ stipules.” The lateral 
portions grow rapidly, and overarch the more slowly growing, circinate apex of the 
leaf, in the manner already well known. 
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