$48 -— | REV. GEORGE HENSLOW ON THE 
bundus, and tripartitus in a line whose equation is z—4y 4-6—0 ; and, lastly, the species 
puse circinatus, cenosus, and hederaceus lie in a line whose equation is y—y=4*. 
- The question, however, arises, What is the significance of these facts ? 
First, we may observe that the number of veins varies with the size of the petals and 
the amount of yellow colour, or “ guide,” at their base, as well as with the number of 
stamens ; therefore, generally with the conspicuousness of the flower. And as glands are 
well developed in the petals of the larger flowers, we may safely assume that such are 
adapted to attract insects, and so secure cross-fertilization. On the other hand, as the 
veins of the petals, as well as their yellow bases and the number of stamens, decrease, so 
the flowers become proportionately less conspicuous, and are more probably self-ferti- 
lizing, as they certainly are according to my observations in R. hederaceus. 
Hence I would infer that R. heterophyllus (25, 9)f, R. peltatus (30, 9), R. fluitans- 
(18, 14), stand at the head of the three groups, and are cross-fertilized, all having large 
flowers, On the other hand, the R. Drouetii (9, 5), R. tripartitus (6, 8), R. hederaceus — 
(7, 8) stand respectively as the last of each group, and which have very small flowers and 
are probably self-fertilizing. "The intermediate forms of each of these three groups will 
represent gradations possibly in each individual ease, being more or less liable to be 
intererossed, but yet have acquired a corresponding less or greater facility in self- 
fertilization. j 
Two species of this order are mentioned by Mr. Darwin as producing plenty of seed 
under a net, viz. Adonis e@stivalis and Ranunculus acris. R. bulbosus, R. acris, and 
R. repens, according to Müller, agree with R. flammula, which he describes in detail, 
with figures (Befrucht. &c. p. 114). The facts recorded exactly correspond with my own. 
observations in summer, that the anthers dehisce centripetally ; the outer stamens spread 
out towards the petals, the carpels being at that time quite immature, but are fully ` | 
developed before the last series of stamens have shed their pollen. B. muricatus has the : 
stamens reduced to about ten, and the carpels fully matured, while the first two or three 1 
anthers only were dehiscing. I found no honey in the glands of the petals. The flowers 
are small and doubtless self-fertilizing. Certain differences obtain in the position of the 
line of dehiscence, so that while R. bulbosus dehisces laterally, R. >». repens and R. flammula 
are more inclined to be extrorse. “As a general rule, it would seem that extrorse anthers 
are specially concerned in intercrossing, but may by no means prevent self-fertilization; _ 
for the petals receiving the pollen from such anthers close at night, and so throw it on ` 
to the carpels. R. sceleratus and R. hederaceus, which have a reduced number of stamens — 
—a common feature in self-fertilizing { flowers—are certainly homogamous. The petals 4 
are frequently, but not always, without honey; while the filaments bend down upon the ` 1 
carpels, so that the anthers are close pressed upon the stigmas. This is the usual position - 
of the stamens in self-fertilizing polyandrous or regular flowers f. It is particularly well — 
` * R. Lobbii, a new species added by Hiern from N. America, and intermediate between these last two forms and ` ` 
the aquatilis group, has the same equation; for he records the number of veins to be 3, and the number of stamens 
from 5-to 9. If, therefore, 7, the equation is e—y=4. 
-t These numbers are that of the stamens (25), and that of the veins in the petals (9). 
t I noticed in a branch of Crateegus owyacantha that every flower with incurved stamens had set its fruit, whereas 
every flower with the stamens ae’ had failed to do so. This observation needs corrobora tion for any general, ` ` 
zation, 
