he antineuritic B, and the antiscorbutic C.

Until very recently, the investigations of vitamines have dealt exclusively
with their relation to human nutrition; although it has been generally
believed that the vitamines themselves are elaborated only by plants. It
was generally recognized, however, that those plants, or parts of plants,
which are capable of very rapid growth or metabolic changes, such as germs,
spores, leaves, etc., are generally the richest source for vitamines for
animal needs. Hence, there seemed to be considerable basis for the
assumption that the elaboration of these substances by plants is definitely
connected with their own metabolic needs. Recently, investigations of the
functions of vitamines in the growth of plants have been begun. These are
still in progress, but the following conclusions seem to be justified at
the present time: (_a_) Potato tubers appear to contain growth-promoting
substances which are essential to the proper growth of the sprouts. Whether
these are the same substances which are efficient in the prevention of
scurvy in men has not yet been investigated. (_b_) Baker's yeast is
probably dependent upon a supply of vitamines in the medium in which it is
to grow. Yeast itself, after having grown in barley wort, is one of the
most important sources of vitamines for animal uses or for purposes of
investigations of vitamine activity. But it has been reported that a yeast
cell will not grow in an artificial medium which contains all the essential
nutrients for yeast but has no vitamines of other plant origin in it. The
addition of barley wort, containing the vitamines from barley germs, or any
other similar supply of vitamines, induces rapid growth and the storage of
vitamines in the growing yeast masses. (_c_) The growth of many bacteria is
either wholly dependent upon or greatly stimulated by the presence of
vitamine-like substances in the medium upon which the microorganisms grow.
(_d_) _Sclerotinia cinerea_, the brown rot fungus of peaches and plums,
will grow only in a medium which contains, in addition to the essential
sugar, salts, and nitrogenous material, vitamines derived from either the
natural host plant tissues or other plant sources. These may be of two
types (namely, a vegetative factor and a reproductive factor) or two
different manifestations of activity of the same vitamine substance. But
both of these factors must be provided before the fungus can make its
character