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 he 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 281, 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. 
