l82 



ANGIOSPERMAE—DICOTYLEDONES 



Fig. 291. Digitalis purpurea, L. (after Henn. MUUer). (i) Young flower 

 in which the anthers of the long stamens are dehiscing; seen from the right side 

 after removal of half the calyx and corolla. To bring the figure into the natural 

 position it must be supposed twisted round to the right till the arrow is vertical. 

 (3) End of the style of do., enlarged ; the stigmatic lobes are apposed. (3) Some- 

 what older flower, seen from below after removal of the lower part of calyx and 

 corolla. The anthers of the long stamens have lost their pollen, while those of 

 the short ones have dehisced. (4) End of the style of do., seen from the side ; 

 the lobes of the stigma are diverging. (5) Empty anthers and diverging 

 stigmatic lobes of an old flower, seen from below. 



Knuth, only the humble-bee Bombus hortorum L. $, skg., on wild plants in 

 Westphalia and Thuringia, and garden ones in Schleswig-Holstein, Mecklenburg, 



and Pomerania (island 

 of Rugen). Sprengel 

 (besides Thrips), a 

 humble-bee, delineated 

 on his title-page, and 

 probably Bombus ter- 

 rester L. Herm. Miil- 

 ler, 3 humble-bees (i. 

 Bombus agrorum F. j ; 



2. B. hortorum Z. 5 ; 3. 

 B. terresterZ. 5) ; also, 

 as unbidden guests, 2 

 small bees (Andrena 

 coitana K. 5, and Ha- 

 lictus cylindricus F. 5) 

 and 3 beetles (i. An- 

 therophagus pallens 

 01.; 2. Dasytes sp. ; 



3. Meligethes sp.). 

 Loew (Berlin Botanic 

 Garden), the bee An- 

 thidium manicatum Z. 

 $, creeping right into 

 the flowers and skg. 

 Plateau (Ghent Botanic 

 Garden), 4 bees (i. 



Bombus terrester Z. ; 2. B. muscorum F.; 3. Megachile ericetorum Lep.; 4. 

 Anthidium manicatum Z.), a Sphegid (Oxybelus uniglumis Z.), a wasp (Odynerus 

 parietum Pz^, and a Muscid (Musca domestica Z.). H. de Vries (Netherlands), 

 the humble-bee Bombus hortorum Z. 5 (Ned. Kruidk. Arch., Nijmegen, 2. Ser., 

 2. Deel, 1875). Willis (south coast of Scotland), a Nitiduhd beetle (Meligethes sp., 

 freq.), 3 bees (i. Bombus agrorum F., skg. ; 2. B. hortorum Z., do. ; 3. B. terresterZ., 

 do.), and a butterfly (Pieris sp., skg.). 



2102. D. lutea L. (Herm. Miiller, ' Alpenblumen,' pp. 273-5; Schulz, 

 ' Beitrage ' ; Knuth, ' Bloemenbiol. Bijdragen.') — The flower mechanism of this 

 species agrees essentially with that of D. purpurea, but the corolla-tube is so narrow 

 that only the head of a humble-bee can be inserted into it. As it is 13-14 mm. long 

 the shortest-tongued humble-bees (e. g. Bombus terrester Z., with a proboscis 8 mm. 

 long) can only just reach the nectar, while the longest-tongued ones (e.g. B. hortorum 

 Z., proboscis 18-21 mm. long) can do so conveniently. 



Hermann Miiller found the flowers to be markedly protandrous below an eleva- 

 tion of 1000 m. in the Vosges, but in the Suldenthal (igoo-1800 m.) the stigma 

 matured at the same time as the anthers of the short stamens, so that automatic 

 self-pollination took place when insect-visits failed. 



Schulz found markedly protandrous flowers at Bozen, in the Tyrol, self- 

 pollination being thus excluded. In the same place he noticed stocks which 

 bore small female flowers as well as the hermaphrodite ones, and also very rare 

 instances of gynodioecism. 



Visitors. — Herm. Miiller, Schulz, Loew, and Knuth only observed the 



