founded on the Structure of their Seedlings . 31 
4. Tribe Allieae. 
Nine species representing four genera have been examined 
from this tribe. The vascular structure of the hypocotyl 
is much reduced, and is identical in all the species examined, 
except Milla biflora. 
Allium neapolitanum. The seedling A 4 from which the 
sections drawn in Figs. 1-5 on PI. V were cut was very 
young, and the traces but slightly lignified. The two bundles 
of the cotyledon are united by their common protoxylem 
group throughout their course. This protoxylem group 
ABC 
begins to turn outwards early (PI. V, Figs. 1 and 2). The 
plumular traces in seedling A 4 are so embryonic that only 
one protoxylem element is lignified at the first node (PI. V, 
Fig. 3) : in the older seedling B it is clear that two traces 
from the plumule join the stele. Their phloem groups run 
into those of the cotyledonary traces : their xylem will form 
one-half of the xylem plate (PI. V, Figs. 4 and 5 )* When 
the series of sections cut from seedling A 4 is examined with 
attention, it is clear that one protoxylem group of the diarch 
root is derived from the cotyledonary, the other from the 
plumular, traces. Each of the two phloem groups is derived 
from both. 
The method of transition represented in Diagram VII is 
common to all the six species of Allium examined (A. neapo- 
litanum , A. Cepa , A. P or rum, A. serufschanicum , A. asca - 
