268 
Hill and de Fraine . — A Consideration of the 
investigation of which indicates that there is a close relationship between 
the surface of the expanded cotyledons and the total area of the cross- 
section of the bundles, as is shown by the accompanying curve, which 
is a particularly good one with the exception of one point. 
Results of a similar nature have been obtained with the seedlings 
of Acer, but in view of the incompleteness of the investigation, it does 
not appear desirable to give figures in the present communication. 
These observations are corroborated by the work of Salisbury, 1 who, 
in a different connexion, found that, in the case of the extra-floral nectaries 
of species of Polygonum , if the cross-sectional area of the xylem in the 
petiole be divided into the area of the corresponding nectary, the value 
obtained approaches a constant. 
The remaining case is where the cotyledons of epigeal seedlings first 
absorb a copious endosperm and then function as foliage leaves, as in 
Ricinus ; here, all the problems alluded to have to be considered. 
In fact, the size of the seedling, and all which this connotes, is very 
important, and has a direct bearing on the seedling-structure. Our observa- 
tions on the Gymnosperms and Angiosperms led us to this conclusion, and 
we were engaged upon an investigation on this subject when the appearance 
of Comptons important paper on the Leguminosae rendered the continu- 
ance of many of our observations on this particular point unnecessary. 
Attention, however, may briefly be drawn to some of the facts observed. 
1. In large seedlings there is much more vascular tissue as compared 
with small seedlings (see analysis below). 
2. Generally speaking, in large seedlings the number of vascular 
strands is greater ; that is, the lateral cotyledonary bundles persist for 
a greater distance downwards. 
In small seedlings at the base of the seed-leaf petioles a median strand 
only usually obtains. In larger seedlings two lateral bundles also are found 
at this level, whilst in still larger seedlings more than two laterals may 
occur. 
3. In large seedlings the lateral bundles tend to produce a tetrarch 
stage in the hypocotyl ; this tetrarchy may persist almost to the base of the 
hypocotyl and may result in a tetrarch root, e. g. Dahlia. 
In smaller seedlings, tetrarchy, even when it does occur, is always 
transient (see p 261). 
4. Not infrequently, more especially in the case of Angiosperms, the 
main central bundle may bifurcate very high up, sometimes even in the 
blade, as in Allionia and other Centrospermae, and in Lupinus , and the 
halves separate widely and resume their normal orientation, leaving the 
protoxylem in an isolated position. 
1 Salisbury, E. J. : The Extra-floral Nectaries of the Genus Polygonum. Ann. Bot., xxiii, 1909. 
