152 On the Species of the Genus Primula in Essex. 
thickly covered with short bristles or papillae. The anthers 
are attached to the sides of the tube about half-way up, and 
the tube enlarges itself slightly above them. They contain 
pollen of an opaque nature and oblong form. A single grain 
of cowslip pollen, according to Darwin’s measurement, 6 
is 25*400 y long; according to Mr. Bennett, 7 it is 25*400 y 
long by 12*700 y broad ; pollen from the long-styled form of 
the primrose, as given by the same authority, is 22*860 y by 
12*700 y, but some which Mr. Rosling has been kind enough 
to measure was 25*400 y long; Mr. Rosling has also found 
pollen from the same form of P. elatior to measure 22*860 y 
in length by 15*240 y in breadth. 
In the short-styled or “Thrum-eyed” form (fig. 1 b), the 
style is only sufficiently long to support the stigma at about 
half the height of the tube, or almost exactly in the same 
position that is occupied by the anthers in the other form. 
The stigma itself is broader, more depressed, and much 
smoother. The anthers are of the same size as in the long- 
styled form, but are affixed to the sides of the corolla-tube 
at its top or only just within the entrance. The pollen they 
contain is larger, more transparent, and almost spherical. 
Some short-styled cowslip-pollen which Darwin measured 
was 86*285-89*914 y long, thus comparing with the other form 
as 100 to 67. According to Mr. Bennett’s measurement it is 
35*560 y by 25*400 y. The same authority states that pollen 
from the same form of the primrose is 30*480 y by 19*050 y, 
and some which Mr. Rosling measured proved to be 35*560 y 
long. Mr. Rosling finds that the pollen of the short-styled 
form of the oxlip is 35*560 y long by 20*320 y broad. The 
pollen of these three species is seen to be much alike when 
examined under the microscope, being, as Mr. Bennett says, 
“ shortly cylindrical rather than ellipsoid.” Mr. Rosling, 
Mr. Bennett, and myself have all observed that the number 
of longitudinal furrows with which the grains are marked is 
variable. * The unfertilised ovules of the short-styled form 
are smaller than those of the long-styled form. 
There is no difference whatever to be observed in the two 
forms as regards the leaves, root, or “habit” of the plant, 
6 [We have reduced all these measurements, which were given in dis¬ 
cordant fractions of an inch by the several observers, to micromilliinetres 
( = y ; 1000 y = 1 millimetre), in accordance with the simple metric 
system now adopted by the Eoyal Microscopical Society. It is to be 
hoped that all microscopical observers will use the system, and so render 
their micrometer measurements comparable one with another. It will be 
adopted in the future in these ‘Transactions.’— Ed.J 
7 ‘ Popular Science Review,’ April, 1875, p. 113. 
