48 



ANGIOSPERMAEDICOTYLEDONES 



below, with only a short lip on its free margin. In A. palmatum Wall, the spur 

 makes its first appearance as a slight projection ; in A. Napellus L. the lip is 

 elongated and expanded ; in A. Anthofa L. and A. columbinum Nutt. the spur is 

 more prominent, and in A. paniculatum Lam. it is well defined. The spur of the 

 Japanese species A. Fischeri Reichenb. is prolonged and curved inwards like a 

 flamingo's bill; in A. septentrionale Koelle it is drawn out in the shape of 

 a proboscis to a length of 6 mm. ; and lastly, in A. Lycoctonum Z., it is coiled 

 into a spiral of if turns. 



The blossoms of Aconitum are as Kronfeld expresses it ' humble-bee flowers 

 par excellence'. The body of a humble-bee exactly fills the interior of the flower, and 

 if a plaster cast of this be made it will be found to correspond in a remarkable way to 

 the shape of a medium-sized female humble-bee. As a matter of fact, Aconitum is 

 dependent on Bombus, and must become extinct in places where humble-bee visits 



Fig. 17. Stages in Specialisation of the Nectaries of Aconitum (after M. Kronfeld). Nectary of: 

 1. Aconitum heterophyllum Wall, (with no spur). 2. A. palmatum Wall, (with a slight projection). 3. A. 

 Napellus Z.. (with a somewhat larger projection, and a longer lip). 4. A. Anthora L. and A. columbinum 

 L. (with projection still more developed). 5. A. paniculatum Lam. (well-defined spur). 6. A. volubile 

 Pall, and E. villosum Rgl. (with buckle-shaped posterior projection. 7. A. Fischeri Reichenb. (spur 

 curved inwards). 8. A. septentrionale Koelle (spur rolled inwards). 9. A. Lycoctonum L. (spur rolled 

 inwards to a greater extent). 



fail, or where these insects merely rob the flowers by making lateral perforations. 

 The dependence of monkshoods on humble-bees is best made clear by comparing 

 their respective areas of distribution. A glance at the accompanying map (Fig. 18) 

 will show that the area of distribution of Aconitum is entirely included in that of 

 Bombus, while the two are coincident in the head quarters of the genera. In other 

 words, the range of monkshoods is closely related to that of humble-bees. 



101. A. Napellus L. (Sprengel, 'Entd. Geh.,' pp. 278-9; Herm. Muller, 

 ' Alpenblumen,' pp. 137-9; Beyer, 'D. spont. Bewegungen d. Staubgefasse u. 

 Stempel ' ; Knuth, ' Blutenbiol. Beob. a. d. Ins. Rugen,' and other works.) The 

 large upper sepal of the erect flower not only helps to attract insects, but also roofs 

 over and protects the underlying nectaries, stamens, and carpels. The three smaller 

 lower sepals, together with the two lower petals, take part in the work of attraction ; 

 and besides this they serve as alighting-places and platforms for the humble-bees 

 that creep into the flower, and complete the protective investment of the stamens and 

 carpels. The two upper petals are converted into characteristic nectaries, each with 



