On the Species of the Genus Primula in Essex. 181
the following spring witnesses a vast change in the abundance
and luxuriance of the Oxlips. The sudden access of the
sun's light and heat acts as a stimulus which induces
every plant to grow and flower to its utmost. The size of
the plants at once increases, the number of umbels is largely
augmented, the flowers come out finer and often twelve or
fifteen on an umbel, and from a little distance the ground
often appears to be of a fine yellow colour. Monstrosities
and abnormally-developed flowers, leaves, and umbels are
also at once produced. The change wrought by the cutting
down of the wood is, however, not generally seen at its best
until the following spring, when the plants, having had time
to grow, increase still more in size and luxuriance, and
produce larger umbels, with finer and more numerous flowers.
The profusion when in this state must be witnessed before it
can be fully realised. I have never seen anything like the
same effect produced by Cowslips or Primroses.38 The
stimulus generally lasts, I think, until the third year (or
occasionally, perhaps, until the fourth), but all depends upon
the rapidity with which the grasses and other herbage spring
up and smother the Oxlips. As the wood grows up these last
generally revert to their original condition, and the huge
38 On the 15th of April, 1883, I was in Peverill's Wood with my cousin,
Mr. Reginald W. Christy, when he was so struck with the extraordinary
profusion of the Oxlips that he suggested a calculation. We accordingly
selected an area four yards square, which seemed to be a fairly typical
one. Certainly there were many other spots of equal size containing
more plants. On this patch we counted carefully all the plants, and
found that there were 231, or an average of about 14.43 to a square yard.
These bore altogether 723 umbels of all sorts, or an average of about 3.13
to a plant. Certainly this last is a very low average, as we counted no
less than 56 umbels on one plant which was not larger than hundreds of
others that could have been found around. We next found out that the
stimulated part on which the plants grew so thickly measured 88 yards
by 440, so had an area of about 38,720 square yards. Part of this had
been cut the previous winter, and part the one before that. Taking these
figures we found that on this area there must have been about 558,730
plants, with 1,748,824 umbels. From these figures, with the aid of others
in Table IX,. an interesting calculation might be made as to the number
of seeds these plants should produce annually.