1905.| On the Inheritance of Heterostylism im Primula. 583 
of forming a fairly sharp pentagon as in normal flowers, the eye in this type 
is produced as a yellow flush extending over about half of each petal. All 
the strains having this flush are in the condition called by Darwin “equal- 
styled.” The anthers are at the same level as in the long-styled flowers, and 
the pollen grains are small and indistinguishable from those of the long- 
styled. The styles, however, are short and do not reach above the level of 
the anthers.* We at first supposed that the equal-styled plants corresponded 
to the mid-styled type seen in trimorphic species, but this is evidently a 
mistake, and the relations of the three types of trimorphic forms present 
much greater complexity than is met with in Primula. 
Experiment shows that the yellow flush is an ordinary recessive character, 
the ordinary or non-flushed type being dominant. The flush is transmitted 
independently of the length of style or the size of the pollen grains, for it 
may be transferred to the true short-styled or “thrum” type. But when the 
' flush is developed in plants which by gametic composition would be long- 
styled, the style does not pass through the anthers, and the equal-styled 
condition is produced. Why the development of the yellow flush in these 
flowers should entail the reduction of the style, we cannot in any way 
suggest. 
From these considerations it follows that when the equal-styled race is. 
crossed with the true short-styled type, two allelomorphic pairs are concerned, 
viz., short-style (D) and long-style (R); no yellow flush (D) and yellow flush 
(R). Fy is, therefore, short-styled with no yellow flush. FF, has four types, 
viz., short, non-flushed ; short, flushed; long, non-flushed ; long, flushed, which 
latter is the equal-styled, the ratio being 9:3:3:1. The long non-flushed, 
which appears as a new form in Fs, is, of course, made by the recombination 
of the parental characters, and the meeting of the “long” character from the 
equal-styled parent with the non-flushed eye derived from the short-styled 
parent. 
Equal-styled x Equal-styled. 
Four plants were raised by crossing equal-styled plants of the same race, 
and did not differ from their parents. From these were raised 14 more by 
self-fertilisation, again identical with their parents. 
* Occasional flowers, in which the stigma is at the anther-level, may be seen on normal 
long-styled plants. They are usually first flowers, and are especially frequent in 
P. acaulis in early spring. We have never seen a genuine case of mixture of types on 
one plant. 
