24 TRANSACTIONS OF THE [ Sess. LXxIII. 
EXPLANATION OF PLATES. 
Pirate I. 
Photo of a specimen of Acanthorhiza aculeata at the Royal 
Botanic Garden, Edinburgh. (By Mr. Robt. Adam.) 
Puate II. 
Fig. 1. Various stages in the life-history of aerial roots of Acan- 
thorhiza aculeata. 
a. youngest stage—root-cap firmly adhering. 
b. 2nd stage—root-cap a loose tuft. 
ec, complete metamorphosis into a thorn. 
d, a branched root. 
e. an aerial root flattened in its upper portion. 
L.S. of young aerial root. 
a. epidermis (thickened on outer walls). 
b. epidermis under the root-cap. 
c. ner root-cap. 
d. outer root-cap. 
3. Enlarged portion of fig. 2. (Lettering as in fig. 2.) 
4, L.S. of an older root showing the peeling off of both outer 
and inner root-caps in layers. 
5. T.S. of the axis of a branched aerial root. A T.S. of the 
axis of an unbranched root (fig. 10, a) would be 
similar. 
. epidermis. 
. protective sheath (Schztzhiille). 
. outer cortex. 
. Inner cortex. 
. endodermis. 
xylem tracheids. 
. phloem. 
pith. 
. aerenchyma with thickened cells at intervals. 
6, 7, 8 (corresponding to figs. 10, 6, c, d). Suecessive stages 
across metamorphosed aerial root showing loss of 
aerenchyma and hardening of tissue. (Lettering 
as in fig. 5). 
9. T.S. across flattened base of aerial root. (Lettering as in 
fig. 5.) 
k. cortical aerenchyma. 
, pith aerenchyma. 
to 
mPa hyeras Ss 
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