800 DISCUSSION ON WHEAT : 
wheat or Hinkorn (Triticum monococcum) ; further the two wild wheats, 
Triticum cegilopioides and Triticum dicoccoides. The macroscopic charac- 
ters mentioned are, however, correlated with anatomical differences in the 
structure of the shell or pericarp of the grain, which still more accentuate 
the separation of the wheats proper and the Spelt wheats. From this 
standpoint the Polish wheat, which generally is treated as a distinct species, 
has to go with the wheats proper. Those are the principal kinds as they 
present themselves to the practical man without consideration of their taxo- 
nomic value. At present they are rather definite and distinguishable units, 
whatever their place and relative position in the evolution of the wheats 
maybe. It need only be added that the various Spelt wheats differ more from 
each other than do the wheats proper. Those ten wheats, however, are 
not only fairly well definable, but they are also constant in the sense that 
we cannot turn Soft wheat into Hard wheat, or Spelt into EKmmer; 
nor has it been proved so far that the two wild wheats can be transformed 
into their assumed cultivated representatives, as we can, for instance, con- 
vert the wild carrot into the garden carrot. But too much stress must not 
be laid upon that, as Triticum agilopioides, the assumed primitive form 
of the EKinkorn, has not been much experimented with, whilst Triticum 
dicoccoides, the supposed Emmer, was only rediscovered quite recently— 
having been known before solely from a single herbarium specimen—and is 
approaching now only its second harvest in the experimental grounds at 
Poppelsdorf, Bonn. In valuing the affinities of those wheats and tracing 
their descent, we have therefore to rely on the varying degrees of their 
structural resemblances, the nature of the differentiating characters, the 
presence or absence of intermediate forms, other than hybrids, and on analo- 
gies. We have seen that the wheats are divided into two groups by what 
is no doubt a practical difference of the highest order: the looseness or 
tightness of the grain in the husks, combined with the toughness or brittle- 
ness of the spindle on the one hand and the thicker or thinner grain shell 
on the other. These are three characters, each by itself, as characters in 
grasses go, apparently of considerable taxonomic value; but if we consider 
their part in the economy of those plants and the constancy with which they 
occur side by side, it becomes clear that they are really very closely corre- 
lated and behave functionally like one character. Among the wild grasses 
effective dissemination is provided for by a great variety of contrivances, 
and generally regulated so that the grains are dispersed singly or nearly so 
and at the same time protected by some covering until germination sets in. 
In the two wild wheats this is secured by the breaking up of the spindles 
on maturity, releasing thereby the individual one- or two-grained spikelets, 
and by the permanent enclosure of the grains in the husks. We find the 
same conditions in the grasses which are generally admitted as the primitive 
forms of rye and barley. In cultivated rye and barley the spindles are 
tough, and in rye and certain kinds of barley, the naked barleys, the grains 
are loose in the husks and separate easily, while in the other barleys the 
grains together with their special husks (flowering glume and pale) are 
loose in the spikelets. But although they are loose they are not loose 
enough to fall out very readily or without the application of mechanical: 
pressure, such as is applied in threshing. This enormously facilitates reap- 
ing, and, where the grains are loose, their subsequent separation from the 
husks; it determines to a great extent the economic value of these cereals, 
while the same conditions would naturally be disadvantageous or even fatal 
to plants in their natural states. And what is true of the cultivated and 
the wild ryes and barleys is mutatis mutandis true of cultivated and wild 
rice and of the cultivated and wild millets. If we now apply the same 
reasoning to the wheats of the tenax group—+that is, the wheats with tough 
spindles—this character, with its correlations, loses practically all its value 
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