EL A TINE AE HYPERICIN EAE 



XVIII. ORDER ELATINEAE CAMB. 



203 



There is only one plant included in this order, of which the flowers have been 

 studied as regards pollination. 



145. Elatine L. 



507. Elatine hexandra DC. Vaucher says that automatic self-pollination 

 takes place in the small reddish-white flowers of this species, the anthers dehiscing 

 introrsely, and shedding pollen directly upon the three stigmas. 



XIX. ORDER HYPERICINEAE DC. 



This order is represented by the genus 



146. Hypericum L. 



The flowers are rendered conspicuous not only by the usually large, bright 

 yellow corolla, but also by the similarly coloured branched stamens (described as 

 'bundles'), and the three styles. They are homogamous pollen flowers. The 

 glands on the calyx in many species keep away creeping insects. The flower 

 mechanisms of the various species agree as regards size, number of stamens and 

 possibility of automatic self-pollination, with those of 



508. H. perforatum L. (Herm. Miiller, 'Fertilisation,' pp. 139-40 ; Kirchner, 

 ' Weit. Beob.,' II, pp. 211-12; Kirchner, 'Flora v. Stuttgart,' p. 325 ; Knuth, 'Bl. u. 

 Insekt. a. d. nordfr. Ins.,' pp. 49, 1 52, ' Weit. Beob. 



ii. Bl. u. Insekt. a. d. nordfr. Ins.,' p. 232, ' Bluten- 

 biol. Beob. a. d. Ins. Riigen,' ' Bloemenbiol. 

 Bijdragen.') In the flowers of this species the 

 three spreading styles are situated between the 

 three bundles of filaments. The anthers dehisce 

 upwards the innermost first and do not usually 

 touch the stigmas, which are on the same level, 

 so that cross- and self-pollination alike depend 

 upon insect-visits. When anthesis is over, the 

 petals and stamens are drawn inwards, the stig- 

 mas being thus generally brought into contact 

 with the anthers, which are still covered with 

 pollen, so that automatic self-pollination takes 

 place if insect-visits have failed. 



Visitors. Hermann Miiller (H. M.) in Westphalia, Buddeberg (Budd.) in 

 Nassau, and myself (Kn.) in Schleswig-Holstein and Pomerania, have observed 

 the following. 



A. Coleoptera. Chrysomelidae : 1. Cryptocephalus sericeus Z., po-dvg. (H. M.). 

 B. Diptera. (a) Bombyliidae : 2. Anthrax flava Mg., po-dvg. (?) (H. M., Thuringia); 

 3. A. maura Z. (H. M., Thuringia) ; 4. Argyromoeba sinuata Fall., vainly searching 

 for nectar (H. M.) ; 5. Bombylius canescens Mikan., skg. (H. M.). (J>) Empidae : 

 6. Empis livida Z., do. (H. M.). (c) Muscidae: 7. Musca sp. (H. M.). (d) Syrphidae: 

 8. Ascia podagrica F., po-dvg. (H. M.) ; 9. Eristalis aeneus Scop. 5, po-dvg. (Kn., 



Fig. 61. Hypericum perforatum, L. (after 

 Herm. Miiller). Flower seen obliquely from 

 above. a, a, a, the three stigmas. 



