HETEROSTYLY 45 
I do not think that this is a chance arrangement, but an adaptation of Nature, 
though I am not now in a position to indicate the object of it.’ Sprengel was 
therefore acquainted with Dimorphism?, but its significance was first made clear 
by Darwin (see p. 8). Vaucher was the first to observe the Trimorphism of Lythrum 
Salicaria (1841, Hist. phys. des plantes d’Europe, II, p. 341), and it was afterwards 
noticed by Wirtgen (Verh. d. naturh. Ver. fiir Rhein]. und Westfalen, v, 1848, Pp: 7). 
In the large majority of cases Heterostyly is associated with other differences 
between the two forms of flower than unequal length of style and stamens. In 
dimorphous flowers, for example, the pollen-grains of the long-styled flowers are 
considerably smaller than those of the short-styled ones, while the stigmatic papillae 
of the former are considerably longer than those of the latter. 
TOLLE oss 
IN 
Tot 
“a 
wii & 
iy 
1 2 
Fic. 3. Prémula acaulis, Jacg., a plant with dimorphous flowers. (Longitudinal section) 
twice natural size. 
(1) Long-styled form. (2) Short-styled form. 
0 0 Wy a7, 
3 4 5 6 
Relative sizes of pollen-grains— ‘ Relative sizes of stigmatic papillae— 
(3) Of the short-styled form. (5) Of the long-styled form. 
(4) Of the long-styled form. (6) Of the short-styled form. 
[(3)-(6) Highly magnified.] 
In some cases of dimorphism there is also a noticeable dissimilarity between the 
two forms of flower in regard to size and conspicuousness. The long-styled flowers 
of Primula longiflora and minima, for example, possess a larger and more conspicuous 
limb to the corolla than the short-styled, while in Primula auricula and glutinosa the 
opposite is the case. In the former two species the short-styled flowers are capable 
of self-pollination, as are the long-styled ones of the other two. Kerner, after 
1 According to Loew, ‘Einf. in d. Bliitenbiologie’ (p. 55, note), Dimorphism was discovered 
almost simultaneously by Sprengel, W. Curtis (‘ Flora Londinensis,’ I. Edit. 1777-87), and Persoon 
(Usteri’s Annalen, 1794, Part 2). The last two both made the discovery in Primula, 
