66 MR. It, H. COMPTON: AN INVESTIGATION OF THE 
ILI. In this column is indicated the type of germination, whether epigeal 
(E), hypogeal (H), or an intermediate condition in which the cotyledons 
hardly rise above ground (H-E). 
IV. The length of the hypocotyl is here expressed in millimetres, the 
limits being the external collet and the base of the cotyledons or the 
cotyledon tube. These figures can have only an approximate significance, 
as the length of the hypocotyl varies much according to conditions ; they 
express more accurately the relative than the absolute magnitude of different 
seedlings. The measurements are for the most part taken from an average 
of my own seedlings ; these are recorded even when they show discrepancies 
from those given in certain species by Lubbock (1892). 
In the hypogeal species this column is not usually filled. 
V. Here is given the diameter of the hypocotyl. Where only one number 
is given it indicates that the hypocotyl is of uniform diameter throughout ; 
where two numbers, separated by an arrow, are quoted, the first number 
refers to the diameter at the external collet, the second to that at the summit 
of the hypocotyl. In the case of hypogeal seedlings the diameter is taken 
immediately below the cotyledons. When a prominent collar is developed 
at the base of the hypocotyl (Acacia, &c.) the diameter is taken just above 
this. 
VI. The dimensions of the cotyledon lamina. The first figure refers to 
its length, the second to its breadth, and when a third figure is given it refers 
to its thickness ; the maximum dimension being taken in each case. 
VII. In this column are given the facts as to the number of protoxylems 
in the root and the type of symmetry on which the transition is effected. 
When a single figure is shown here it indicates that the symmetry is con- 
stant throughout. When two or three figures are given, separated by 
arrows, changes in symmetry within the axis are to be understood ; in each 
case the first number refers to a level below that of the second, and this 
again to a level below that of the third: the last number thus indicates the 
symmetry at the node. When two or more figures, separated by commas, 
are given, it is indicated that the number of protoxylems varies in different 
specimens. 
VIII. Here an attempt is made to classify the various kinds of transition 
phenomena in the vascular system. according to the position in the seedling 
at which they occur. It must be understood, of course, that, as there are 
innumerable gradations between the extreme types, such a classification must 
be often arbitrary and largely an expression of personal judgment. Three 
terms are used to express the “level of transition " :— 
“ High."—The greater part of the hypocotyl has a structure almost indis- 
tinguishable from that of a root ; the transitional changes do not 
begin until high up in the hypocotyl, and are incomplete at the 
cotyledonary node. 
