BORAGINEAE 



121 



is at first concave and of a violet colour, but expands later on into a dark- 

 blue, five-lobed star. The corolla-tube is 7 mm. long, and its enlrance is 

 blocked up by five closely apposed pocket-shaped hispid involutions, so as to give 

 protection against rain and unbidden guests (flies). These pouches may be seen 

 externally as transverse slits at the bases of the corolla-lobes. They also play 

 the part of nectar-guides. The stigma is situated immediately below them, while the 

 simultaneously maturing anthers are placed about the middle of the corolla-tube, and 

 dehisce introrsely. Visitors (bees or Lepidoptera) must first touch the stigma, 

 pollinating it if they have come from another flower, and then the pollen-covered 

 anthers, thus effecting crossing. Should insect-visits fail, automatic self-pollination 

 lakes place as a last resort, for the corolla drops off" and the anthers, to which some 

 pollen still clings, are drawn over the stigma. 



Gynomonoeciously or gynodioeciously distributed female flowers have been 

 observed, though rarely, in ad- 

 dition to the hermaphrodite ones. 

 Schulz (' Beitrage ') states that 

 they occur sporadically in larger 

 numbers, and result from the 

 reduction of stamens in a small- 

 flowered hermaphrodite variety. 



According to Schulz the 

 hermaphrodite flowers do not 

 everywhere possess the same 

 mechanism. They are not only 

 of different sizes, but the relative 

 position of stigma and anthers 

 is variable even in flowers on 

 the same stock. Sometimes the 



stigma is higher than the anthers (as in the description already given from tlie 

 accounts of Sprengel and Herm. Miiller, and verified by myself in Rugen), sometimes 

 lower, or at the same level. Warming even noticed heterostyly in Denmark, while 

 Schulz remarked it, though not in a pronounced form, in Germany and the Tyrol. 

 Kirchner describes well-marked dimorphism for garden plants, the style of one form 

 being nh mm. long, and that of the other 8 mm. Where the stigma is at the same 

 or a lower level than the anthers, automatic self-pollination is more easily possible 

 than in long-styled flowers, for it can take place simply by the fall of pollen. 

 Generally, however, this possibility is not made use of, for insect-visits are extremely 

 numerous. 



Visitors. — Herm. Miiller gives the following list for Westphalia (W.) and 

 Thuringia (T.). — 



A. Hymenoptera. {a) Apidae: i. Anthophora aestivalis Pz. 5, skg. (T.) ; 

 2. A. quadrimaculala Pz. 5 and J, do. (T.) ; 3. Apis mellifica L. 5, numerous, skg. and 

 po-cltg. (W. and T.) ; 4. Bombus agrorum F. 5, 5 and S, skg. (W. and T.) ; 5. B. 

 lapidarius Z. S and 5, do. (W.) ; 6. B. pratorum L. 5, 5 and S, skg. and po-cltg. (W. 

 and T.) ; 7. B. muscorum F. (W.) $ and 5, skg. (W. and T.) ; 8. B. sylvarum Z. ^, 

 skg. and po-cltg. (W.) ; 9. B. tristis Seidl. 5, skg. (T.); 10. Coelioxys conoidea III. J, 

 do. (T.) ; II. Melecla luctuosa Scop. 5, do. (T.); 12. Osmia caementaria Gerst. J, 



Fig. J71. 

 (i) Flower seen 



Aiichtisa oylcinaiis. L. (after Herin. ^l;ilk'r). 

 from above. (2) Do. after removal of half the 



cal}'.\ and corolla, seen from the side. «, nectary. 



