70 
Swamp Plants and Respiration. 
In Proc. Australian Assoc. Adv. Science, i, 327 (1888) the late Dr. Joseph Bancroft 
read a paper, " Respiration in the roots of Shore-plants," which, like a good deal of 
his work, was in advance of his time, and it remained, at least in Australia, little added 
to for a number of years. He took cognizance of the aerating roots, or breathing-roots, 
or pneumatophores of certain Mangroves, and " knees " in certain Conifers. Their 
function is to supply oxygen to the trees anchored in mud. 
He also took cognizance of certain adventitious, or aerial, or stilt-roots in 
Mangroves. It is not always convenient to strictly separate the two classes of roots. 
For example, at p. 328, Dr. Bancroft refers to Rhizophora mucronata, the Red Mangrove, 
and says, " it throws up no aerial (breathing) roots, but those sent downward, tripod-like 
(stilt-roots), apertures are seen with elevated edges, circular, one-twentieth of an inch 
in diameter, and filled with reddish-brown powder." At Plate xxiii he figures these 
stilt-roots in this species. 
Schimper, p. 401, says, " The species of Rhizophora do not possess special pneuma- 
tophores, yet the upper part of their stilt-roots that are above the mud perform the same 
function." 
The stilt-roots have even an economic value. The aerial roots, being very 
elastic, afford good material for bows, of which the Fijians avail themselves. (Seemann.) 
Arched roots are similarly used by Solomon Islanders in Port Curtis, district, Queensland. 
C. Hedley (Proc. Roy. Soc. Qld. v, 11). 
Dr. Bancroft, at p. 327, began his observations on Avicennia ojficinalis, the common 
Grey Mangrove (found pretty well round the Australian coast), near Brisbane, and 
Plates xxv and xxvii represent Mangroves from Moreton Bay. He refers to an earlier 
paper submitted to the Royal Society of Edinburgh, which was not published, and 
following is an abstract of the same. 
Prof. Dickson read a paper by Dr. Joseph Bancroft on respiration in the roots of certain shore 
plants. His observations referred chiefly to the remarkable rootlets of Avicennia. These rootlets grow 
vertically upwards from the larger roots which extend themselves horizontally in the mud of salt-water 
creeks. The mud bank around the stem is covered by a brush of such rootlets to a distance of from 4 to 
yards from the bole of the tree. This brush, by entangling debris, protects the bank from destruction by 
stream or tide. The rootlets are studded with pits or pores emitting powdery matter which consists of 
cells, and which may be observed floating on the surface of the brackish water of the creek. These pores 
he regards as corresponding to lenticels, and he finds that when air is forced into the cut end of a rootlet 
it issues by the pores. Henne he conjectures that the function of the pores is to contribute to the aeration 
of the plant, a view coinciding with that held by several botanists as to the lenticels, which they regard as 
structures affording, like stomata, a communication between the atmosphere and the interior of the plant. 
(Nature, Vol. xxv, 403 [1882]). 
In his 1888 paper Dr. Bancroft goes on to say : 
Amongst various things that interested me. a white powder floating on the brackish water 
presented itself as ;>n object of inquiry. This powder looked at a distance like the male Vnllix-nfi-ia flower, 
but n closer inspection it was observed to issue from openings m 1 lie uerial mots of neighbouring Avicennia 
trees, tlii- hiiliitat of which is restricted to the iiiuddv banks ol s;i.||, \v;ilcrs. Some of these upright roots 
in rapid growth, found casting off the white powder, I drew up, together with the horizontal white pithy 
parts that were in process of extension to an unoccupied mudbank. Having secured a number of specimens, 
