490 DH. MARIE STOPES ON BENNETTITES sCOTTII, 
forming a single frond is an area roughly L:2x 2 cm., while that of the 
present species is only *5 x ^4. 
The number of leaflets in each group, /. e. in each single frond, is not 
precisely determinable because the groups are not quite complete ; the most. 
complete in appearance has 10 pinnules on either side, neatly packed and 
overlapping, but higher up as many as 15 pinne are to be seen, and this 
number is probably incomplete. As Wieland (1906) pointed out, the number 
of pinne in the leaves of a given species of living eyeads varies so greatly 
that exact computations of the pinnæ in the fossil forms do not yield distinctive 
data, The indications are that the fronds of the present species were not 
only small, but had relatively few pinnæ. It must not be forgotten, however, 
that a species with many pinnæ like Cycas circinalis for example, have on 
the early leaves of their sprouting stems less than a fifth of the number of 
pinne present on a leaf produced in maturity. 
Details of Leaflet Structure. 
In a general way these fossil pinnæ are unlike those of Cycas, but like 
those of the other genera of cycads and like those fossil species described by 
Wieland (1899, 1906, 1916) in having a series of well marked, parallel 
bundles, all through the mesophyll of the leaf, each bundle surrounded by a 
well developed sheath and accompanying sclerenchyma. The highest number 
of bundles observed in one pinna in the present fossil, is 23 ; the pinnæ cut 
lower down having as fewas 5or 6. The general plan of the middle portions 
of the leaflets can be seen in fig. 12, Pl. 20, and of the corners of the leaflets 
in fig. 11. 
These leaflets, like those described by Wieland, have a strong upper cuticle 
and sub-epidermal tissue, and the upper differs from the lower surface of the 
leaflet. Beautiful as are the American specimens, all the anatomical details 
are not yet clear for the leaves of this family, and the present species throws 
some light on a doubtful feature of the leaf as described by Wieland, 
Details of the tissues of these leaves will consequently be given. 
The upper epidermis, as can be seen in figs. 10 & 11, Pl. 20, and text-fig. 3, 
is regular and well developed, with thickened outer walls and a cuticle. In 
the central portions of the leaflet the epidermis and the thickened tissues 
beneath it seem less developed than elsewhere, of. PI. 20: fig. 12 and text- 
fig. 4 with fig. 11, Pl. 20, and text-fig. 3. So far as I can observe, neither 
stomates nor hairs are present on the upper surface. This agrees with the 
generalisations of Thomas and Bancroft (1913) on the group. 
Beneath the epidermis, particularly developed at the corners of each 
leaflet, where it is several cells thick, is a thick-walled hypoderm, see /, 
text-fig. 3, and figs. 10 & 11, Pl. 20. A palisade seems to be slightly, 
but not very noticeably differentiated from the more irregular mesophyll, 
