I 1 2 
THE PLANT WORLD. 
physiological units, which in the end must be the basis for the distinction 
of the systematic units may best be designated by the term of ‘ unit charac¬ 
ters ’ (p. 249). Their internal nature is not yet known. The fact receives 
repeated emphasis that both species and their characters are discontin¬ 
uous.” 
The study of hybrids affords means for a better distinction between 
elementary species and varieties, for the two behave in quite different 
ways when subjected to crossing. The cases considered are, “ the crosses 
between elementary species of the same or of very narrowly allied syste¬ 
matic species, on the one side, and on the other, . . . to the crossing of 
varieties with the species, from which they are supposed to have sprang 
by a retrograde modification.” Crosses of different varieties of the same 
species t and of progressive varieties are omitted. 
In the inter-crossing of varieties, as in normal fertilization, all unit 
characters are paired (even though some may be dormant in either of 
the parents), and the differentiating marks of either parent appear in the 
hybrid. When elementary species are crossed the differentiating mark of 
one finds no mate to pair with in the other, and the hybrid does not em¬ 
body all the features of both parents. The first case, following the ter¬ 
minology of McFarlane (1892) is a bisexual cross, the second, a unisexual 
cross. Unisexual unions show the diminution of fertility universally 
known as marking hybrids. Several examples are given. 
Crosses between varieties (bisexual crosses) do not give rise to con¬ 
stant hybrids, but to hybrids that split in successive generations, usually 
according to the now well-known law of Mendel. Instances occur among 
clovers, snapdragons, violets, sugary varieties of corn with starchy varie¬ 
ties, et cetera. 
The unit-characters “ are represented in the hereditary substance of the 
cell nucleus by definite bodies of too small size to be seen, but consti¬ 
tuting together the chromosomes. For these material bodies, deVries 
adopts Darwin’s term of “pangens” When a new elementary species 
arises it is recognized by the possession of a new unit character, which is 
the expression of the formation of a new pangen. 
Ever-Sporting Varieties. —Accidental anomalies, however they may 
arise, are commonly called sports. Sporting is a constant character of 
some plants, and varieties “ of pure and not hybrid origin, but which sport 
in nearly every generation,” are termed ever-sporting varieties. Striped 
flowers, as the striped larkspur, are examples of this type. “ Here the 
variability is a thing of absolute constancy, while the constancy consists 
in eternal changes! ” Most of the so-called variable types in horticulture 
belong to this group. The variation is limited in extent by two extremes. 
Other examples than the striped varieties are fasciated branches, pitchers, 
split leaves, and peloric flowers. 
Experiments were made with a snapdragon Antirrhinum majus luteum 
rubro-striatum, which has three types; (a) pure yellow, (b) pure red, 
(c) stripes of various width. There are no pure yellow racemes, but close 
inspection always reveals stripes. On the other hand the red flowers are 
a separate type within the striped variety, the gap between pure red and 
