218 AN GIOSPERMAE DICOTYLEDON ES 



170. Cratoxylon Blume. 



556. C. formosum Bentham et Hook. f. Darwin (' Different Forms of 

 Flowers ') states that the species possess dimorphous flowers. 



XXV. ORDER GERANIACEAE DC. 

 1. Tribe Geranieae. 



Literature. Herm. Muller, 'Fertilisation/ pp. 149-60; Knuth, 'Grundriss d. 

 Bliitenbiol.,' p. 37. 



The flowers are usually bright in colour, and very frequently red. They differ 

 greatly in size in the various species, and with increasing inconspicuousness, there is 

 proportionate diminution in the number of insect visitors, but increased probability 

 of automatic self-pollination. In most species nectar is secreted by the outer sides of 

 the bases of the five external stamens. Almost all the flowers belong to class C 

 as regards concealment of nectar, but certain species may be placed in class H, not 

 because the nectar is more deeply situated, but because the flowers hang in such 

 a way that only very expert visitors can reach it. The flowers are mostly pro- 

 tandrous, rarely homogamous or protogynous. The greater the probability of 

 insect-visits the more marked is the dichogamy. Besides hermaphrodite flowers, 

 there are smaller female ones in some species, distributed gynodioeciously, as a rule. 



171. Geranium L. 



Flowers protandrous, rarely protogynous (G. dissectum and G. pusillum), with 

 concealed nectar secreted by the outside of the bases of the five inner stamens. 

 Some of them are bee flowers. Jordan states that in the erect flowers belonging 

 to class C, insect visitors alight on the petals, while in the case of the pendulous 

 flowers belonging to class H they settle on the stamens and pistil. 



557. G. palustre L. (Sprengel, 'Entd. Geh.,' pp. 335-7; Herm. Muller, 

 'Fertilisation,' p. 149; Schulz, ' Beitrage,' I, p. 28; Kirchner, 'Flora v. Stuttgart,' 

 P- 335 5 Knuth, 'Bloemenbiol. Bijdragen.') The markedly protandrous flowers of 

 this species spread out their purple-red petals with paler claws to form a surface 

 30-40 mm. in diameter, which is turned to the sun. The nectar-guides are dark 

 lines on the corolla, converging to the middle of the flower. Nectar is secreted 

 in abundance by five glands on the outer side of the bases of the five inner stamens. 

 Hairs on the bases of the petals serve to protect the nectar, and prevent the access of 

 rain-drops. The five inner stamens ripen first, and then the five outer ones, and 

 only when these have shed their pollen do the stigmas that have so far been closely 

 apposed spread out and project from the middle of the flower. After dehiscing 

 all the stamens bend outwards so far that automatic self-pollination is impossible. 



Besides hermaphrodite flowers, Schulz has observed female ones distributed 

 gynodioeciously, or more frequently gynomonoeciously. He also distinguished 

 between large- and small-flowered varieties of the hermaphrodite flowers. 



Visitors. Herm. Muller (H. M.) in Westphalia, and myself (Kn.) in Schleswig- 

 Holstein, have observed the following. 



A. Diptera. (a) Musctdae: 1. Arithomyia sp., skg. (H. M.). (5) Syrphidae: 

 2. Eristalis tenax ., skg. (H. M.); 3. Helophilus pendulus Z., do. (Kn.); 4. Meli- 



