HYDROPHYLLACEAE 115 



rises into a series of prismatic tubes, each bounded by a pair of longitudinal folds and 

 the midrib of a petal. 



Visitors. — Loew (Berlin Botanic Garden) observed the honey-bee and the 

 humble-bee Bombus terrester Z. 5. vainly trying to suck. He regards as the true 

 pollinators insects that can probe the flowers without alighting, i.e. Bombyliids or 

 hawk-moths. 



592. Nemophila Nutt. 



1950. N. maculata Benth. (Willis, J. Linn. Soc, Bot., xxx, 1895.) — The 

 very conspicuous flowers of this species are protandrous. 



Visitors. — In England, more particularly bees. 



593. Hydrolea L. 



1951. H. spinosa L. (Willis, op. cit.) — Willis states that the odourless blue 

 flowers of this species are adapted to self-pollination, and that this is effective. 



594. Wigandia H. B. et K. 



1952. W. caracasana H. B. et K. (Francke, Inaug. Dissert., Halle, 1883.) — 

 Francke states that this species is protogynous. 



LXXI. ORDER BORAGINEAE DESV. 



Literature. — Herm. MuUer, 'Fertilisation,' pp. 408-23, ■ Alpenblumen,' pp. 

 265-7; Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' p. 107, ' Grundriss d. Bliitenbiol.,' 

 pp. 76-7; Loew, Ber. D. bot. Ges., Berlin, iv, 1886, p. 152; M. Giirke, ' Boragi- 

 naceae,' in Engler and Prantl's 'D. nat. Pflanzenfam.,' IV, 3 a, pp. 78-9. 



A considerable but variable number of flowers are associated in cymes, often of 

 scorpioid character. They may be rotate, tubulo-campanulate, or infundibuliform, 

 and secrete nectar from the receptacle immediately below the ovary. It is stored in 

 the corolla-tube, the throat of which is often provided with scale-like appendages 

 promoting concealment. The native German species consequently belong to flower 

 class C, especially the sub-class H, for the visitors are almost exclusively bees. 

 Crossing by insect-visits is ensured or favoured by dimorphism in Pulmonaria ; by 

 marked protandry in Echium and Borago ; by exsertion of the stigma in Cerinthe, 

 Symphytum, and Anchusa; and in Lithospermum, Echinospermum, Myosotis, and 

 Omphalodes by contraction of the corolla-tube, securing that stigma and anthers 

 shall be touched by opposite sides of the proboscis of an insect visitor. Should 

 insect-visits fail, the facility with which automatic self-pollination may take place in 

 a given species is inversely proportional to the conspicuousness of the flowers and 

 their richness in nectar. Cerinthe, Echium, and Pulmonaria, owing to their great 

 conspicuousness and large amount of nectar, receive such a large number of visits 

 that automatic self-pollination is excluded. On the other hand, according to 

 Hermann Miiller, the small scantily nectar-secreting flowers of Lithospermum 

 arvense Z., Myosotis intermedia Link, M. collina Hqffm., and so forth, are very 

 rarely visited by insects, and almost always pollinate themselves. There are 

 numerous transitions between these two extreme cases. 



