70 PRESIDENTIAL ADDRESS 
In 1881, I brought a matter of some interest to botanical 
students before the Philosophical Society, and seeing that, as 
far as | am aware, there is no paper printed on the subject, I 
take this opportunity of mentioning it. In May of that year I 
was examining a brackish waterhole under the shade of an 
Avicennia tree, and observed that the surface of the water was 
strewn with a white flour-like powder. Seeking the source of 
the powder, I found it issuing from the rootlets of the Avicennia 
tree. These rootlets are pithy and full of air, and rise out of 
the mud at the foot of all Avicennias, or “‘ white mangroves.” 
I took rootlets with me for microscopic examination, and found 
numerous spots casting off white flakes of corky cells. Thinking 
that this had something to do with the circulation of air in the 
pithy rootlets, I attached a rubber cap, and on immersing the 
end of the rootlet in water, found air could be pressed from 
the cap and made to issue from the spots that were casting off 
floury particles. On comparing these spots with other similar 
excrescences, I found them to correspond to what are called 
lenticels, and, to make a long story short, that the corky incrus-° 
tations on peaches and other trees are respiratory organs. My 
account of this discovery I sent to Professor Balfour, of Edin- 
burgh, and he thought it sufficiently important to read it be- 
fore the Royal Society of that city. Professor Balfour shortly 
afterwards died. The communication was commented on by 
the scientific papers of the time, and was mentioned in Nature. 
Some other botanist in France had just come to the conclusion 
that the lenticels were «rating organs, and in consequence of 
his claim to priority and my friend’s death, the communication 
was not published by the Royal Society of Edinburgh, neither 
was my manuscript returned. I propose to submit my original 
paper on this subject to you ata future meeting, especially as 
this discovery has thrown important light on the function of 
lenticels and tends to clear up much that is obscure as to the 
hpysiological import of the extensive development of these 
