the Young Epicotyl in some Ranalean Forms. 163 
Aconitum . Marie has described the adult anatomy in a number of 
species. The vascular system of the stem consists of separate collateral 
strands arranged either on a single circle somewhat unevenly, as in 
Delphinium , or on two or three circles, thus resembling Thalictrum. The 
tuberous rhizome may exhibit a ring of bundles united by a cambium, or it 
may show anomalous structures such as the ring of concentric bundles 
found in Aconitum Author a. 
In external appearance the seedlings of this genus resemble those of 
Ranunculus. There is a tendency to the early formation of tubers. 
Text-fig. 7 . Aconitum Wilsonii. First plumular node. M 1 , l 1 , trace of first leaf ; 
m 2 , median strand of second leaf. 
Anatomically, the seedlings are noteworthy in possessing small leaf- 
trace strands, so that the primary xylem is slight in extent. To compensate 
for this a cambial ring is instituted very early, but the amount of xylem 
formed is not great and there are large principal medullary rays which 
define the bundles even after the formation of secondary thickening. 
A. Wilsonii. The seedlings of this genus are glabrous and have 
a fairly large, long-stalked, reniform foliage leaf. At an early stage there 
is a tuberous swelling of the hypocotyl and lower part of the epicotyl. 
A rather young seedling, with a single expanded foliage leaf, showed 
an almost complete cambial ring at the first plumular node (see Text-fig. 7). 
M 3 
