180 
ON THE DESCENT OF THE SAP. 
too damp for their tubers, which, if taken out of the ground and kept 
dry for a month or so, might perhaps expedite their flowering in 
summer. 
We got one plant of the hoitong, the Cydonia Japonica of 
Persoon. This plant had been introduced several years before by 
Mr. Slater, but repeatedly lost by being treated as a stove plant. 
(To be continued .) 
Hyde Park Corner, 20 th April, 1836. 
On the Descent of the Sap. — Sir, — -I feel much surprised 
that, after all the methods you have taken to excite an investi¬ 
gation of the merits of the physiological theory which you have 
promulgated, that as yet not one of our writers upon this interesting 
science has taken the least public notice of your remarks. Many 
reasons might be assigned for deterring individuals like myself from 
calling in question the validity of your opinions; but no apology 
can be pleaded by those who, whatever may have been their own 
personal investigations, have at least joined issue in the opinions of 
others, and published and inculcated these opinions for the purpose 
of instructing us in the science of our art. Scarcely has the smallest 
work emanated from these scientific instructors, that contains not, as 
a recommendatory set off, a high-flown compliment respecting our 
stupidity and prejudice, and yet they have allowed the opinions of a 
practical man, with whom, according to their own showing, we are 
most apt to identify ourselves, to pass unnoticed and unchallenged, 
although these opinions have a direct tendency to demolish the whole 
of that theory which they have inculcated. For myself, I pretend not 
to possess that intimate acquaintance with the subject which could 
qualify me for passing a proper judgment; and, indeed, I much doubt 
if ever I shall arrive at the knowledge of a defined general principle 
applicable to all cases of vegetable development, since the more I have 
investigated the phenomena of vegetation, the more have I become 
convinced that different tribes are regulated in a certain degree by 
systems as diversified as their nature. Approving, how r ever, of your 
anxious desire to have your opinions investigated, I venture to make a 
few remarks and inquiries, confident that you will exercise your 
accustomed good feeling and indulgence, and give us a farther detail of 
your views, as at present we possess not sufficient data to pronounce 
that you are right or wrong. 
Waiving minor details, I conceive that the peculiar views you enter¬ 
tain have a reference chiefly to the motion and properties of the sap, 
and the existence of a newly discovered member named the indusium or 
vital envelope. 
