Anatomy of Adenophorus sarmentosus — Wilson and Rickson 
117 
have a diameter of only V2-V3 of the average 
of the elements of the inner phloem. In the 
outermost tissue of the stele, outside the narrow 
strip of outer phloem, occur the numerous large 
cells of the pericycle (Fig. I, 5). 
The stele of the petiole is circular in cross 
section and is surrounded by flat endodermal 
cells which separate it from the heavily sclerified 
layers of the cortex. The center part of the stele 
is occupied by the single xylem strand which, 
in cross section, is roughly reniform (Fig. 
1, 7). The protoxylem elements are in groups 
of about six at each of two points forming the 
adaxial lobes of the strand. The xylem is sep- 
arated from the phloem by two or three layers 
of irregularly shaped, nucleated parenchyma 
cells. The phloem area is made up of one or 
two rows of tiny, thin-walled cells, and sur- 
rounds the entire xylem core except at its 
protoxylem poles. Between the phloem and the 
endodermis occur the large, nucleated, thin- 
walled cells of the pericycle containing plastids. 
The cortex is clearly differentiated from the 
epidermis and is composed of six to eight layers 
of thick-walled sclerenchyma cells. The thick- 
ness of the cell walls of the cortical cells in- 
creases gradually, so that the cells in the outer- 
most layer have extremely thick walls. There 
is also a gradual decrease in the diameter of 
the cells toward the periphery of the cortex. 
The large thin-walled cells of the epidermis are 
subtended by a layer of slightly smaller thin- 
walled cells containing numerous plastids which 
separate the cortical sclerenchyma from the 
epidermis itself. In the lateral marginal wings 
of the petiole the epidermis, containing occa- 
sional pairs of guard cells, is subtended by a 
tissue of loosely arranged parenchyma cells with 
large intercellular spaces. 
The adaxial laminar surface lacks stomata. 
In face view the epidermal cells are approxi- 
mately 1-3 times as long as wide, and their 
general outline is somewhat oblong. The longi- 
tudinal walls are moderately wavy (Fig. 1, 
10). The abaxial laminar surface is characterized 
by more irregular cells, generally with pro- 
nounced undulate walls (Fig. 1, 11). Both 
epidermal surfaces bear scattered suberect or 
erect hairs. The epidermal hairs are two- to 
four-celled, uniseriate, simple or frequently 
branched, and with a large, reddish-brown ter- 
minal cell (Fig. 1, 12). 
In cross section, the cells of the upper epi- 
dermis are seen to have irregular vertical pro- 
jections which reach below the epidermal layer 
itself and come in contact with the spongy tis- 
sue of the leaf (Fig. 1, 9). The lower epider- 
mal cells rarely display such projections. The 
mesophyll is composed entirely of irregular, 
loosely arranged, spongy parenchyma cells with 
large intercellular spaces. The round sori are 
borne terminally on the veins. The sporangia 
have a single row of cells at the base of the 
stalk, and an annulus with 11-13 thickened 
bow cells (Wilson, 1959^). The spores are 
green, tetrahedral, trilete, without exospore, and 
have an average measurement of 34 X 12 fx 
(Selling, 1946). 
The roots have a diarch stele with two pro- 
toxylem groups, one at each end of the xylem 
tract (Fig. 1, 6). The one- or two-layered 
phloem surrounds the xylem except at the pro- 
toxylem poles, and is separated from it by a 
layer of parenchyma cells. The endodermal cells 
are small, and thin-walled, and were difficult 
to observe in our preparations. This many- 
celled endodermis is surrounded by the inner 
layer of the two layers of heavily sclerified 
cortical cells. The outer two or three layers of 
cortical cells are conspicuously thinner-walled. 
DISCUSSION 
In general, the structure of Adenophorus 
sarmentosus agrees with the observations of 
Nozu (1958-1960) made on species of Micro- 
polypodium ( Xiphopteris ) , Scleroglossum, and 
Grammitis. On the basis of these studies and 
of general systematic surveys (Holttum, 1954; 
Copeland, 1947), the solenostele of A. sarmen- 
tosus seems to be characteristic of the rhizome 
of most of the Grammitidaceae, although in 
some groups a dissected solenostele is not un- 
common. The absence of an internal phloem 
in the younger portions of the rhizome of Ade- 
nophorus sarmentosus is noteworthy. A similar 
medullated protostele was described in Micro- 
poly podium okuhoi by Nozu. The stele of A. 
sarmentosus, however, soon becomes soleno- 
