326 Lee. — Seedling Anatomy of Certain Sympetalae. II. 
to scale. The roots of those marked (1) are diarch throughout, those distin- 
guished (2) are tetrarch throughout, while those marked (f-) are first tetrarch } 
but finally become diarch. The difference in size between Arctium majus 
or Crupina Crupinastrum and Baeria coronaria need not be emphasized, but 
it must be noted that all these possess the same type of seedling structure. 
Again, compare Arctium majus or Crupma Crupinastrum with Silphium 
perfoliatum ; the first two are diarch, the last tetrarch throughout, though 
one can hardly say that the difference in size warrants such a difference in 
vascular anatomy. An examination of the seedling of Bidens pilosa serves 
not only to emphasize this point, but also to throw light on another, i. e. the 
relation between the amount of vascular tissue present and the type of 
seedling structure. 
If, as has been cautiously advanced by Hill and de Fraine (6), there is 
a real relation between the size of the organ and the amount of vascular 
tissue present, it follows that organs of the same size should (if the 
vascular tissue be arranged in the same way) possess the same amount 
of vascular tissue, not in a transverse section, but in the whole organ ; and 
further, that in an organ like the hypocotyl, which presumably, in the 
ordinary case, everywhere performs the same function, the vascular tissue 
present in any transverse section should equal in amount the vascular 
tissue in any other transverse section of the same area. 
To take the first case. In the seedling of Fagus sylvatica, Hill and 
de Fraine appear to pit the area of vascular bundles in a tiansverse section 
of the seed-leaf against the surface area of the cotyledon. Now, as the 
vascular bundles decrease in size towards the apex of the seed-leaf, the area 
of the bundles depends very much on the position of the transverse section, 
and it is improbable that one would be able to select the corresponding 
section in a large number of seedlings. Furthermore, the relation between 
the amount of vascular tissue in a transverse section and the surface area of 
the leaf is not at all obvious. It appears, on the other hand, that the total 
amount of vascular tissue present in the organ should be taken into account, 
and should be correlated either with the cubic contents of the leaf or with 
the surface area. Here again, it is almost impossible to make precise 
measurements. A cursory examination, however, of almost any species 
will reveal the fact that while the type of venation remains the same, the 
number and extent of the smaller bundles vary greatly, even when the 
leaves are of the same size. 
With regard to the second point raised above, in most hypocotyls, 
measurements show that in successive transverse sections of the hypocotyl 
the amount of vascular tissue is approximately the same, or it decreases 
slightly towards the base of the hypocotyl. This is what one would expect 
on any theory postulating a definite connexion between size of organ and 
the amount of vascular tissue present. In the hypocotyl of Bidens pilosa , 
