4° 



ANGIOSPERMAE—DICOTYLEDONES 



two processes. Above the angle of the claw, on its upper side, there is a slit 

 protected by a cover. The nectar is secreted internally on the under side of the 

 bend, and is concealed in the cavity of the tubular claw. The cover closes by 

 elasticity after it has been raised, and lies between two projections which prevent 

 it from being displaced. (See Fig. 14, B,C,D.) 



87. N. arvensis L. (Sprengel, 'Entd. Geh.,' pp. 280-9; Terraciano, 'Intorno 

 alia strutt. fiorale ai process. d'impoUinaz. in ale. Nigella,' Boll. Soc. bot. ital., 

 Firenze, 1892, pp. 46-51; Knuth, ' Bloemenbiol. Bijdragen.') — Sprengel has given 

 a very thorough account of the structure of the flower. The description is one of 

 the most signal achievements of this great investigator. 



The sepals are whitish below and bright blue at the tip. The small nectariform 

 petals are brownish or blue on the upper side, with two white or yellow-green 

 transverse bands. Their limbs present whitish or brown transverse striations : the 

 process of the nectar-cover is whitish and brown. It is further to be noted that 

 the white filaments are marked on the inner surface — not far from their insertion — 

 with a white spot that can be dimly seen by transparency on the outside. The 



Fig. 14. Nigella^ L. (From nature.) A. Nigella damascena L. Flower towards the end of the 

 second stage: the styles have curved spirally downwards, and are in contact with the anthers (a), which 

 are still covered with pollen, so that automatic self-pollination necessarily follows. (Natural size.) i?, C, 

 D. Nectaries of N. Sativa, N. damascena, and N. arvensis (x 3J). The form of the nectaries B and C 

 appears to be somewhat variable. 



flower thus possesses a series of ten alternating light and dark rings, which serve 

 as annular nectar-guides, by which insect visitors (bees) are directed to one nectary 

 after another. 



Above the nectaries there are eight groups of stamens, each consisting of six 

 members, one behind the other. When the flower opens all the forty-eight stamens 

 are erect. On the first day of flowering the outermost member of each group 

 curves downwards and outwards, which causes the dehiscing side of its anther to 

 face downwards, so that the dorsal surface of an insect sucking from the nectaries 

 must necessarily be dusted with pollen. On the second day the eight outermost 

 stamens — which are now withered — assume a horizontal position, so as to lie upon 

 the sepals, and their place is occupied by the eight stamens next in order. On 



