458 ANGIOSPERMAE—DICOTYLEDONES 



315. Cucurbita Juss. 



Very large yolk-yellow monoecious flowers ; with nectar secreted as in Bryoniii. 



1084. C. Pepo L. (Warnstorf, Verb. bot. Ver., Berlin, xxxviii, 1896.) — The 

 male flowers of this species mature somewhat earlier than the female ones, and 

 their stalks are rather longer, so that they are first visited. 



Warnstorf states that the calyx and corolla of the male flowers are united at 

 the base, where they support a cup-shaped disk with a tumid edge. Abundant 

 nectar is secreted. This cup is completely covered by the column of stamens, and 

 is only accessible by means of two to four openings at the bases of the filaments. 

 The anthers are extrorse. The pollen-grains are very large, yellow, spherical, 

 prickly; covered with a thin layer of oil, and therefore extremely adhesive; on 

 an average 163 /x in diameter. 



Visitors. — I observed the honey-bee, very freq., skg., at Kiel ; 2 or even 3 

 bees were often to be seen in one flower. 



316. Sechium P. Br. 



1085. S. edule Sw. — Arcangeli states that in this species there are two nectaries 

 in the base of both female and male flowers. In the latter they are in the form 

 of small narrow, inconspicuous pockets ; in the former they are larger and more 

 conspicuous. The explanation of this is perhaps that insect visitors can only find 

 nectar in the female flowers, while in the male ones they may also obtain pollen. 



317. Ecballium A. Rich. 



1086. E. Elaterium A. Rich. — According to Hildebrand (Bot. Ztg., Leipzig;, 

 li, 1893), this species shows the most varied arrangements of the male and female 

 inflorescences. In autumn the last flowers to appear are solitary and female, which 

 can be fertilized by the pollen of earlier male ones. 



XLVII. ORDER CACTEAE DC. 



Hansgirg states that the numerous filaments of many cactus flowers are alnlo^t 

 equally sensitive on all sides to mechanical stimulation, curving inwards from the 

 corolla towards the stigmas in response, e. g. in Opuntia Ficus-indica Mill., O. Engel- 

 manni Salm-Dyck, O. Camanchica Engelm. el Bigel. and O. Rafinesquii Engdm. 



318. Opuntia Tourn. 

 Flowers mostly large, feebly i)rotogynous, and devoid of nectar. 



1087. O. vulgaris Mill. (=:Cactus Opuntia Z.). (Schulz, 'Beitrage,' II, 

 p. 80.) — The flowers of this species, which is cultivated in South Europe, arc 

 nectarless, and Schulz gives their diameter as 30-40 mm. The outermost perianth 

 leaves are greenish-yellow, while the inner ones are of a brilliant sulphur-yellow 

 colour. In dull weather and at night they bend somewhat inwards. The stigmas 

 aie receptive at the beginning of anthesis. Before the flowers expand the filaments 

 are curved inwards, but afterwards become more or less erect. The anthers are 



