2 99 
of the albumens Vessels of Trees. 
naturally deposited. After ail ineffective struggle of a few 
weeks, the plants became perfectly obedient to my wishes, 
and formed their tubers precisely in the places I had assigned 
them. Many of the joints of the plants during the experi- 
ment became enlarged and turgid ; and I am much inclined 
to believe, that if I had totally prevented the formation of 
regular tubers, these joints would have acquired an organiza- 
tion capable of retaining life, and of affording plants in the 
succeeding spring. 
I had another variety of the potatoe, which grew with 
great luxuriance, and afforded many lateral branches ; and 
just at that period, when I had ascertained the first com- 
mencing formation of the tubers beneath the soil, I nearly 
detached many of these lateral branches from the principal 
stems, letting them remain suspended by such a portion only 
of alburnous and cortical fibres and vessels as were sufficient 
to preserve life. In this position I conceived that if their 
leaves and stems contained any unemployed true sap, it could 
not readily find its way to the tuberous roots, its passage 
being obstructed by the rupture of the vessels, and by gravi- 
tation ; and I had soon the pleasure to see that instead of 
returning down the principal stem into the ground, it remained 
and formed small tubers at the base of the leaves of the 
depending branches. 
The preceding facts are, I think, sufficient to prove that the 
fluid, from which the tuberous root of the potatoe, when 
growing beneath the soil, derives its component matter, exists 
previously either in the stems or leaves ; and that it subse- 
quently descends into the earth : and as the cortical vessels 
during every period of the growth of the tuber are filled with 
