Behind these first outposts, the higher growth came on, and still
farther off the great bulk itself reared skyward, blotting out the
horizon behind, threatening, inexhaustible. It seemed to prod its
precursors, to demand hungrily ever more and more room to expand.

But the creeping of the runners over the first few feet of salt
dwindled to a stop. This caused experienced observers like myself no
elation; we had seen it happen many times before at the encountering of
any novel obstacle, and its only effect had been to make the weed change
its tactics in order to overcome the obstruction, as it did now. A
second rank moved forward on top of the halted first, a third upon the
second and so on till a living wall frowned down upon the salt, throwing
its shadow across it for hundreds of ominous yards. It towered erect and
then, repeating the tactic invariably successful, it toppled forward to
create a bridgehead from which to launch new assaults.

The next day new stolons emerged from the mass, but now for the first
time excitement seized us up in our bobbing post of observation. Not
only were the new runners visibly shorter in length but they crept
forward more slowly, haltingly, as though hurt. This impression was
generally discredited, people were surfeited with optimism; they felt
our reports were wishful thinking. Their pessimism seemed to be
confirmed when the weed repeated its action of the day before, falling
ahead of itself upon the salt; and few took stock in our excited
announcements that the grass had covered only half the previous
distance.

Again the probing fingers poked out, again the reserves piled up, again
the mass fell. But it fell far short of a normal leap. There could no
longer be any doubt about it; the advance had been slowed, almost
stopped. The salt was working.

Everywhere along the entire band the story was the same. The grass
rushed confidently in, bit off great chunks, then smaller, then smaller,
until its movement ceased entirely. That part which embedded itself in
the salt lost the dazzling green color so characteristic and turned
piebald, from dirty gray through brown and yellow, an appearance so
familiar in its normal counterpart on lawns and vacant lots.

The encircled area filled up and choked with the balked weed. Time after
time it essayed the deadly band, only to be thwarted. The glistening
fortification, hardly battered, stood triumphant, imprisoning the
invader within. Commen