Evening star., 1936-04-11

The upbuilding of aristocracies and
their overthrow by revolutions seems 10
be dominant law Of life.
Its application to the vegetable worlo
is found in extensive experiments just
reported by DR.. Frederick A. clements
of the Division of Plant Biology OF the
Carnegie Institution Of Washington.
His experiments and ooserVa.lons
throw light on perplexing problems
among them the origin OF species. Inere
are. DR.. Clements finds, plant COM
munities" adapted to localities Wnlcn
continually are changing as conoIlohS
change, progressing to filter ana ntter
types, and then reverting to the prlmi1lVe
through cataclysIns.
Each successive community, says
DR.. Clements, from lowly moss or hcnen
IN the final forest, owes its acquisition
of territory and its golden age TO the
conquest of the original inhabitants, anu
will in turn be disposSessed by more
powerful invaders The outcome OF eacn
neriod of competition is the dominance
of the best-eouipped community, untli
the incoming prairie or forest puts an emo
IN the waves of invasion and conquest,
owing to the fact that each represents
the highest type of population possible
in the particular climate. ThlS py no
means indicates that competition Is ao-
cent in these communities, but merely
that the ruling class cannot be over
thrown without revolution.
"An accurate census of the prairie re-
veals A tendency for the brilliant flowers
to be replaced by the dominant grasses.
a fate that even overtakes the peas ana
cloyers in spite of their service as nltro-
gen fixers for the entire community.
DIR. Clements studies, he reports to the
carnegie Institution, show clearly tnat
such factors as limited supply OF water
or light will produce striking dinerences
between individuals, not infrequently OF
the magnitude seen in varieties and spe-
cies. This comes about in a single gen.
eration. as a result of direct adaptation.
but as vet there is no adequate PROOF
that these new features can be nxeo,
and hence transmitted to succeeding
generations.
Furthermore" says DR.. Clements, mo
experimental evidence has been obtained
that the minute fiuctuating variations
emphasized by Darwin are accumulated
year by year until they constitute new
species, and it now appears improbable
that this is the case. in plants at least
Even in the prairie, where the stature
and form of the grasses and herbs are
the outcome of thousands Of years OF
competition, it has proved possible to
modify these greatly in a single year by
removing individuals to the point where
the supply is in excess Of the demand
These experiments also have served to
confirm the view that the succession OF
land populations, such as Is exhibited
in a burn, q sand dune, the delta OF
river or an old lava flow, is largely or
wholly a consequence of competition:
One Of the most striking experiments
reported dealt with the so-called "buf-
falo grass" which once covered tne
prairies, and was much in the public eye
at the time of the recent duststorms. IL
played an important part in tying down
the top soil. During the past generation
it has been practically exterminated.
The general opinion has been that this
grass disappeared in the wake OF the
vanishing bison, presumably because OF
some vague bond Of synpathy between