ae. 
306 THE FERTILISATION OF FLOWERS. [PART II. 
another interesting case of an adaptive modification imperfectly — 
attained. ? 
The Rubiacez include more dimorphic (heterostyled) genera t 
than any other order. Darwin (167) discusses many of these 
cases, enumerating seventeen dimorphic genera, in addition to which 
Chasalia, Commers., Ophiorrhiza, L., and Luculia, Sweet, are men- 
tioned by Kuhn (399). Darwin discusses the probable transition — 
from heterostylism to dicecism in Rubiaceze. Mitchella, L., which is | 
normally heterostyled, is in some places dicecious (Meehan, 465). ® 
Asperula scoparia, Hook., and A. pusilla, Hook., two Tasmanian — 
species, were stated by Treviranus (742) to be dimorphic, but | 
according to Darwin the former at any rate is dicecious. Our own : 
Asperula taurina, L., and Galium cruciatum, With., are both — 
andromoneecious, and Sher ardia arvensis, L,, 1S pvndédicecions (605). 
Te 
(at: < 
Orv. VALERIANE 4. 
Delpino in his work on the Artemisiacez rightly insists that the 
calyx in Composite could only become transformed into a pappus 
after the involucral bracts had assumed the usual functions of a 
calyx ; and he considers the Valerianes to be offshoots of the Com- 
positze, which have in part retained this hereditary development of — 
a pappus, and in part have acquired other means of dissemination 
of the seeds by the wind. . 
208, VALERIANA OFFICINALIS, L.1 is distinctly proterandrous. — . 
The florets, in spite of their small size, are rendered conspicuous by. 
aggregation. In each floret the tube is 4 to 5 mm. long, and half 
a millimetre from the base is a small pouch with a green, fleshy 
floor, which secretes and lodges the honey; this is accessible to _ 
numerous insects with moderately short proboscides, especially as 
the tube widens above to a diameter of 2mm,  Insect-visits are” 
numerous and various, and the well-marked dichogamy ensures — 
cross-fertilisation in case of insect-visits. In the first period the 
anthers, covered all round with pollen, in the second the three out- 
spread stigmas, project freely from the flower, and are touched by — 
the feet and under surfaces of insects creeping over the inflorescence 
and by the heads of insects sucking honey from the florets; in the 
second period the anthers are bent away outside the floret. I 
have never seen florets which fertilised themselves ; stigmas which 
* Compare Sprengel, No. 702, pp. 63-65. 
