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Transactions of the Boyal Society of South Africa. 
such species with distichous leaves represent ancient types, or whether 
they show simply a reversal to a more primitive type. 
From the appearance of the specimens as they reached me, it seemed 
that the stem and a portion of the leaves are underground, so that only a 
very small portion of the upper rugose part of the leaves and the inflor- 
escence are exposed,* and Miss Britten later informed me that this is 
certainly the case. 
It does not require much imagination to come to the conclusion that 
the exposed parts resemble, to a large extent, pebbles of stone, and most 
likely the plant derives a considerable amount of protection from its 
partly hypogean habit. I would, therefore, suggest that it has to be 
classed with the so-called " mimicry" plants to which Burchell,t Marloth,| 
and Thiselton-Dyer § have called attention. It would thus be the first 
monocotyledonous plant belonging to this category, but I believe several 
other species of Haiuorthia are similarly protected. H. truncata is not 
the only species of its genus which buries itself to a certain extent under- 
ground. Several species of the sections VenoscB and Betusce do this also to 
a considerable extent. In our species the roots showed decided transverse 
wrinkles, and it is therefore safe to conclude that they are contractile, 
and draw the plant gradually into the ground as the stem elongates at the 
top, while its older portions die off. In the stemless species of Aloe the 
stem is also constantly pulled into the ground by adventitious roots, || 
though this may not show itself in specimens cultivated in pots. Thus in 
our species the stem and the greater portion of the leaves remain buried, 
while only the rugose portion of the leaves protrudes aboveground. The 
underground parts of the leaves continue, however, to act as assimilating 
organs, and the median channels on the back and front of the leaves no 
doubt help to facilitate an interchange of gases, while arrangements 
against excessive transpiration are ample. Stomata, which, as in other 
members of the genus, are sunk below the surface, are found scattered 
chiefly in the lower portion of the leaves. They decrease towards the 
apex, and are quite absent on the flat top. Longitudinal sections show 
that, while the assimilating tissue is arranged along the side-walls, the 
apex and centre are quite free from chlorophyll. There is a strong cuticle 
covering the whole of the leaf. It is especially thick in the upper third. 
The small tubercles in the upper flat portion are several-celled and 
impede, to a certain extent, the light entering the leaf, as I could make 
* Similar largely underground foliage leaves are found in Mesemhrianthemum 
(§ Sphceroidea) and in Bulbine mesemhrianthemoides. 
f " Travels in the Interior of Southern Africa," i., p. 210. 
+ Trans. S. Afr. Phil. Soc, xv., 1904, p. 97; xvi., 1905, p. 165 ; xviii., 1907, p. 281. 
§ Annals of Botany, xx., p. 124. 
II A. Berger, I.e., p. 4. 
