Jone 1910.| BOTANICAL SOCIETY OF EDINBURGH 85 
saturated, the water-table rising to the surface. In summer 
the clay as a whole always remains moist, while the loam 
may get very dry. 
M. Christy + says of the distribution of the two species 
of Primula that though P. vulgaris occurs all round the 
area occupied by P. elatior, the two do not overlap to 
any extent. In the woods of West Cambridgeshire, how- 
ever, this sharp distinction does not hold in most cases. 
Some of the woods have only a single species, but in most 
the two species occur and largely mixed together. Gener- 
ally where P. elatior occurs it is the more abundant if the 
soil conditions are suitable. 
The factors determining the distribution of P. elatior 
seem to be mainly amount of lime and water content. It 
does not seem able to flourish if either gets below or above 
a certain amount, and the range does not seem very great 
in these woods. 
It flourishes most, apparently, on the clay with a lime 
content of about 4 per cent., and a water content high in 
spring and never falling much below 30 per cent. at any 
time of the year. However, it cannot stand a very wet 
soil: in those woods where the soil remains nearly saturated 
throughout the year, though the lime content may be quite 
sufficient, P. elatior does not flourish, and P. vulgaris takes 
its place. 
Should the soil be drier, again, P. elatior ceases to 
flourish—its lower limit would seem to be about 25 per 
cent. Thus in some woods and parts of others which have 
better drainage there are few or no plants of P. elatior, but 
large quantities of P. vulgaris. 
P. elatior is extremely intolerant of non-calcareous soil. 
On the loamy patches of the Boulder Clay it is entirely 
absent, though P. vulgaris is present in quantity. The 
absence in this case is not due to the lowering of water- 
content alone, and in parts of the loam the requisite 
amount is present at all times of the year, but no oxlips 
occur. 
P. elatior is not a plant that demands a very dense 
degree of shade. After the coppice in the woods has been 
cut it increases in quantity very rapidly and flowers with 
1 «J. Linn. Soc.,” xxxiii., 1898. 
