REPRODUCTIVE ORGANS IN THE PRIMULACER. 91 
be due to the absence of insects ; but it is to be remembered that 
we have here, as already stated, experimental observations afford- 
ing similar evidence. These, conjointly with the long-continued 
observations of Mr. M‘Nab, fully justify our suspicions respecting 
the sterility of the long-styled form under cultivation. The phe- 
nomena of sterility, however, are truly so capricious, that but for 
the remarkable sexual relations of the dimorphic species of Pri- 
mula (including, as some suppose, a possible tendency to the 
dicecious structure), such observations were entirely superfluous ; 
and this the more especially, as I am now aware, from observa- 
tions on native specimens in the Edinburgh University Herbarium, 
that the long-styled forms do produce seed. Those who believe 
that dimorphism is a step towards diceciousness, instead of attri- 
buting sterility in the present case to certain unnatural conditions, 
will naturally be inclined to suppose that by man’s artificial treat- 
ment the development of the plan of nature has been accelerated, 
the phenomena of reciprocal dimorphism exhausted by the func- 
tional impotence of the female element of the hypothetical male, 
and the final step made to the complete separation of the sexes. 
I have hitherto spoken of two forms only of the Primula Auri- 
cula, viz. the long- and short-styled ; occasionally, however, in this 
as in other truly dimorphic species, a third form occurs with sta- 
mens and pistils of an equal length. This trifling structural dif- 
ference of the latter is connected with very important functional 
differences, as we find it yields much more seed when self-fer- 
tilized than either homomorphie union. In the following table 
I will illustrate this by giving the results from a self-fertilized 
umbel of an equal-stamened and -styled form; besides these, I 
have also given the results from unions between the latter and 
the long- and short-styled forms. 
Taste II. — Primula Auricula. 
| toso 2 
leg 188.5 i 
EASHET 
| sh | Seis E 
[me | as | a8 | 
Equal-stamened and -styled form by own pollen......... | 14 | 9 | 272 
Short-styled union—pollen from the above ............... | 12 7 59 
Long-styled union—pollen from the above ............... | 12 9 47 | 
The sexual powers of this equal-stamened and -styled form have 
a twofold interest: first, when viewed comparatively with the pure 
homomorphie unions of the other forms ; and secondly, when the 
LINN, PROC.—BOTANY, VOL. VIIT. I 
