520 ANGIOSPERMAE—DICOTYLEDONES 



1205. C. florida L. — Kerner states that this species displays the same kind of 

 geitonogamy as C. Mas. 



iao6. C. suecica L. (Knuth, ' Bloemenbiol. Bijdragen.') — I had the oppor- 

 tunity of examining the flower mechanism of this species in the Dravitholz, between 

 Tondem and Lugumkloster (Central Schleswig), at the beginning of July, 1891. 

 The four yellowish bracts, streaked with reddish veins, play the part of petals, so 

 that a pseudo-flower with a diameter of nearly 2 cm. is formed. Each bract is 

 I cm. long ; one pair of opposite bracts are somewhat broader than the others, 

 i. e. 8 mm. as compared with 6. From the middle of this pseudo-flower spring 

 about twenty truly hermaphrodite flowers, arranged in an umbel. They are red in 

 colour, only 2 mm. long, and borne upon peduncles of the same length. Sepals and 

 petals are recurved. The style of each flower, with its stigma, is i mm. high, while 

 the four diverging stamens are 2 mm. in length. An insect alighting on the umbel 

 must therefore first touch the stigmas, and then the anthers, so that cross-pollination 

 is effected when a visit is made to a second flower. 



I could not decide whether the flowers were protandrous or homogamous with 

 persistent stigmas, for it was only towards the end of anthesis that I was able to 

 examine them ; most of the anthers had dropped off, while the stigmas were still 

 receptive. 



Failing insect-visits, automatic geitonogamy is possible by the spreading of the 

 stamens so as to touch the neighbouring flowers. 



Visitors.— I observed a few hover-flies — Eristalis arbustorum /,., and Helophilus 

 pendulus L., po-dvg. 



LI. ORDER CAPRIFOLIACEAE JUSS. 



Literature. — Hermann IMuller, ' Fertilisation,' pp. 289-99; Knuth, 'Grundriss 

 d. Blutenbiol.,' pp. 61-2. 



As Hermann Miiller has remarked, the members of this order are extremely 

 variable in regard to their flower mechanisms. Lonicera Caprifolium possesses 

 a corolla-tube as much as 30 mm. long, and its nectar is therefore only available 

 to hawk-moths with the most elongated proboscis ; L. Periclymenum, with a corolla- 

 tube about 20 mm. in length, gives access to long-tongued bees as well as to 

 hawk-moths ; L. caerulea is a humble-bee flower ; L. nigra is a bee-flower ; while 

 the nectar of L. tatarica and L. Xylosteum (corolla-tube only 3-7 mm. long) is 

 accessible to bees and also to certain flies ; Symphoricarpos is regarded by Hermann 

 Miiller as a wasp-flower (I observed chiefly bees, but also hover-flies as visitors), and 

 Lonicera alpigena is similar ; the funnel-shaped corolla of Linnaea also allows insects 

 with a moderately short proboscis to reach the nectar ; Viburnum possesses fully 

 exposed nectar, and is therefore pollinated by short-tongued insects (flies and 

 beetles), which also visit to some extent the nectarless species of Sambucus; Adoxa, 

 finally, with its perfectly flat exposed layer of nectar, attracts minute insects of various 

 orders (flies, Neuroptera, beetles). Automatic self-pollination is chiefly rendered 

 possible in species which receive the smallest number of insect-visits; cross- 



