98 INTRODUCTION 



all serving to attract animals that effect pollination, so that they are described as 

 nuptial, other nectaries are sometimes to be found on the vegetative organs of plants, 

 which serve totally different purposes, and have at most but an indirect relation to the 

 crossing of flowers. These organs, which are described by Delpino as exlra-nuptial, 

 by Kny as asexual nectaries, serve to allure ants, which afford protection to the plants 

 against the attacks of other animals, and so form a kind of body-guard. Sprengel 

 ('Entd. Geh.,' p. 356) noticed these extra-floral nectaries, and also the visits of ants 





Fig. 15. Various forms of Nectar-guides in Erodium Cicuiarinm. (From Nature.) (i) The two 

 upper petals are relatively shorter, broader, and coloured a darker red, with two or three dark veins ; the 

 two lower lateral ones are relatively long;er, narrower, and coloured brighter red, with a dark mid-rib ; the 

 fifth petal (the middle of the three lower) is the longest, narrowest, brightest, and is veinless. (2) The two 

 upper petals have each three long veins ; on each of the two lateral lower petals there are one or two 

 somewhat branched lines ; the fiftll (middle lower) has a central vein. (3) The two upper petals have three 

 veins that are in part branched and possess a dark basal spot ; the three lower have each three veins. 

 (4) Three petals have three partially-branched veins and a dark basal spot (largest in the middle one) ; 

 two petals have each only three veins. (5) The two upper petals have each three branched veins and 

 a large dark basal spot ; of the three lower petals the two lateral ones have each three veins and a smaller 

 dark spot ; the middle one has three veins. (6) The two upper petals have a spot that covers almost the 

 entire surface, as well as the three veins ; the two lateral of the lower petals have three veins, and 

 a medium-sized spot, the middle lower petal has also three veins and a somewhat smaller spot. (Cf. 

 Knuth, 'Blumen und Insekten auf den nordfriesischen Inseln,' p. 52.) 



to Vicia sepium : ' This plant provides nectar for insects not only in its flowers but 

 also on its stipules. These have on their under side a small cavity, which is not 

 of so dark a green as the leaves, but is slightly yellowish and contains a drop of 

 nectar. The great wood-ants search eagerly for this fluid.' The significance of 

 the extra-floral nectaries as secretory organs serving to attract protective ants was 

 first recognized by Delpino (1873): but his investigations are outside the actual limits 

 of flower pollination, and so are only referred to here. 



According to what has been just stated, nectaries may be classified as — 



i. Nuptial : 



r. Intra- floral. 



2. Circum-floral. 



3. Extra-floral. 



ii. Extra-Nuptial. 



Even in pollen flowers a marking like a nectar-guide is sometimes found on 

 the petals, and this has been described as a pollen-guide. This term does not seem 

 to me to be correct, for the mark always points to the place where nectar should 

 occur, not to where pollen is found. I would therefore propose the term pseudo- 

 nectar-guide. The erect yellow standard of the pollen flower Ononis natrix, for 

 example, possesses red streaks running towards the base of the flower. 



Sap. As Sprengel (' Entd. Geh.,' p. 3) long ago pointed out. Orchis latifolia 

 and O. Morio have the typical structure of nectar flowers, but contain no nectar. 



