| THE AUSTRALIAN NATURALIST. 
eee e still stands. He was an ancestor of Mr. F. W. Hixson, + 
ee of Elizabeth Bay Point, to whose kindness I am indebted 
' for the loan of the volumes.  . 
THE ADVENTITIOUS AERIAL -(APO-GHOTROPIC) 
ROOTS OF CYCADACEAEH, 
(By A. A. Hamilton.) 
An interesting series of seedlings: of Macrozania 
spiralis, Mig. (Zamia spiralis, R.Br.), in which. these 
structures were more or less developed, was recently col- 
lected at Ettalong Beach, Woy Woy, by Miss Hilda Butler. 
Aerial roots are not uncommon in this family, but as they 
arise in the seedling stage and do not remain long on the 
plants, only occasionally appearing above the ground line, 
their occurrence has not been frequently observed. Sachs, 
A Text Book of Botany,’”’ in a figure illustrating the 
_ germination of Macrozamia spiralis (p. 487), depicts rudi- 
mentary structures, representing these roots on a seedling 
‘plant of this species. Marloth, ‘‘Flora of South Africa,’’ 
figures (p. 99, pl. 15), a peculiar coral-like formation of 
such roots, ascending from the tap-root, a little below the 
crown of a seedling of Hncephalartos villosus, Lehm. Dis- 
cussing these coralliform roots, Marloth (p. 95) says:— 
“Tt is not certain what the function of these roots may 
be, but they probably assist in the nutrition of the plant, 
thus functionally corresponding to the mycorrhiza of some 
Confers (Pinus, Podocarpus).’’ A peculiarity: of these 
roots, according to Marloth, is that in a certain cir- 
- cular layer of their tissue they harbor masses of a green. 
alga (Nostoc punctiforme). The habit of sheltering algae 
in aerial roots is also attributed to Stangeria paradoxa, 
Moore, another member of the Cycadaceae. Algal sym-- 
biosis, in the roots of Cycadaceae, was noted in the Aust. - 
Naturalist, Vol. 2, p. 194, by Mr. W. M. Carne, one of 
our members who is now on active service. 
