380 BOTANICAL GAZETTE [DECEMBER 
The midrib of the leaflet has a very thick-walled epidermis, 
and a few hypodermal strata of collenchyma on both faces, border- 
ing on a water-storage tissue with many aggregated crystals. 
There is no endodermis, but a closed sheath of stereome, which 
surrounds a stele of several collateral mestome strands, all of which 
turn the leptome toward the periphery, and with the hadrome 
bordering on a central pith. The pith is thin-walled, and contains 
some few crystals, aggregated as well as single, rhombic. The 
- much thinner lateral veins are more or less imbedded in the meso- 
phyll, and contain only one mestome strand, surrounded by a 
chlorophyll-bearing parenchyma sheath. The structure of the 
rhachis and the petiole is identical with that of the midrib, thus 
containing a typical stele of several mestome strands, a sheath of 
stereome, and a cortex of which the peripheral strata are collenchy- 
matic. 
Juglans nigra 
SEEDLING 
In the Juglandaceae the cotyledons are hypogeic in all the 
species examined, with the exception of Pterocarya caucasica C. A. 
Mey., which germinates with the cotyledons above ground. It is 
a marked characteristic of the Dicotyledons that the cotyledons are 
epigeic, and it is only in a relatively few families that they remain 
underground, serving only as storage organs. Subterranean coty- 
ledons, however, are known from trees, shrubs, and herbs, terrestrial 
as well as aquatic, but the Nymphaeaceae is the only family in 
which all the species, so far as known, germinate with the cotyledons 
underground and inclosed within the seed. In the other families 
subterranean cotyledons are characteristic of some certain groups, 
for instance, Vicieae, or genera: Phryma, Sanguinaria, Caulo- 
phyllum, Panax, Melittis, Collinsonia, Quercus, Castanea, Aesculus, 
Sassafras, Citrus, Aegle, Mangifera, Persea, Prunus, etc. While 
in some genera the majority of the species germinate with epigeic 
cotyledons, some exceptions occur, for instance in Amemone, 
Oxalis, Clematis, Aristolochia, Phaseolus, Rhamnus, etc., where some 
few species have the cotyledons constantly subterranean. 
Characteristic of the seedlings with hypogeic cotyledons is the 
generally strong development of the primary root. In the Nym- 
phaeaceae, Nuphar, Nymphaea, and Victoria, however, the primary 
