1919 



AMERICAN BEE JOURNAL 



407 



observation, experimentation. Spren- 

 gel's answer was reached by the first 

 two; the new answer sought by Dar- 

 win was to be obtained through the 

 third. For eleven years he put the 

 question direct to the plants them- 

 selves; fertilizing them by their own 

 pollen; cross-fertilizing them; raising 

 and re-questioning their offspring. 

 More and stronger progeny from 

 crossing was the answer. 



The popularity that Linnaeus had 

 given to characterizing and classify- 

 ing living things, was transferred by 

 Darwin to studying their structure 

 and doings. Sprengel's idea fell up- 

 on barren soil, Darwin's was cultiva- 

 ted with care and skill. 



Two men, Mueller, a German, and 

 Delpino, an Italian, stand out most 

 prominently among a multitude who 

 observed and wrote and pictured the 

 marvels of flowers and insect harmo- 

 nies for a generation. All did excel- 

 lent work in furnishing new details 

 and corroborations, but Darwin had 

 answered the question as to the what 

 and the why of the nectar of flowers. 



But there is nectar that is not pro- 

 duced in flowers. Look at the queer 

 spots in the angles betwen the veins 

 on the under side of a Catalpa leaf, 

 when it is young, or at the little gob- 

 lets on the stalk of a cherry or peach 

 or snowball leaf, or at the pin-head 

 spots on a trumpet-creeper or pae- 

 ony calyx, and you may see glands 

 there that secrete a sweet fluid. Bees 

 may not care for it, but wasps or 

 ants do. The cotton plant has such 

 nectar glands on the outside of the 

 cluster of bracts about each blossom, 

 and on the back of its leaves. 



In a very few cases such "extr.i- 

 floral" nectar serves the same pur- 

 pose as that within the flowers; but 

 generally it does not lead to fertili- 

 zation. Delpino called the nectir 

 that leads to fertilization "nuptial" 

 nectar, and the other "extranuptial." 



In the seventies of the last century 

 an English mining engineer, Belt, 

 well known in the ore regions of Col- 

 orado, was marooned by his profes- 

 sion on a mining property in Nica- 

 ragua. Using his eyes took the 

 place with him of tennis, or of dissi- 

 pation, which is the white man's bane 

 in the tropics. He saw that a certain 

 sort of ants cut the leaves of trees 

 into bits, which they take into their 

 nests, and that roses and other intro- 

 duced plants fared hard with these 

 leaf cutters unless they were pro- 

 tected by aromatic oils, as various 

 kinds of citrus leaves are, or in some 

 other way. 



Belt did not fail to notice that the 

 ants visit extrafloral nectaries in 

 numbers. In the case of those on 

 some acacias he found the ants very 

 pugnacious. I confess that in Guate- 

 mala I have preferred, myself, to go 

 around a bush or a grove of such 

 acacias with their ant guards. As 

 with Sprengel's geranium hairs, these 

 nectaries unfolded question after 

 question. 



In Belt's case, the tips of the aca- 

 cia leaflets ripen up also into little 

 fruit-like bodies that the ants gather 

 and take into their nests; and they 

 make these nests in the stipules that 



flank each leaf and sometimes are 

 shaped like a pair of small buffalo 

 horns. It is an interesting undertak- 

 ing to get the ant census of an aca- 

 cia twig of this sort. The danger 

 may not be as great, but it is as real 

 and perhaps as painful as in taking 

 the census of a mountain valley 

 noted for moonshine traffic. 



Belt drew the conclusion that 

 extranuptial nectar, sometimes sup- 

 plemented by solid food and shelter, 

 is of use to the plant that provides it 

 by maintaining a bodyguard of ants 

 on plants that otherwise would risk 

 defoliation and injury by leaf-cutters 

 or grazing animals; much as Spren- 

 gel and Darwin found an explanation 

 of nuptial nectar in the benefit of 

 insect pollination of the flowers. 



This is the simple story of nectar, 

 simply told, as it has been seen by 

 many observing and thinking men. 

 But it is not a story free from com- 

 plications. Our blue violets rarely 

 set fruit from their showy nectar- 

 bearing flowers; but their main reli- 

 ance for seed is on flowers produced 

 below the leaves, and these do not 

 open, but are self-fertilized. The 

 beautiful Poinsettia, with its bril- 

 liant red bracts and large cups over- 

 flowing with thick nectar, does not 

 fruit in West Indian gardens any 

 more than it does in our green- 

 houses at Christmas time. And irre- 

 sistibly pugnacious as the acacia 

 ants are, those that visit our pae- 

 onies and cassias and other plants 

 do not usually more than protest 

 mildly if we molest the plants that 

 they are on. 

 Are the explanations of Sprengt-1 



The Guatemalan ant acacia. 



and Darwin, and of Belt wrong? No 

 others that are at all satisfactory 

 have been offered. 



When one stops to think of it, the 

 secretion of nectar is an unusual 

 phenomenon. Sugar is made within 

 plants and it does not leak from 

 them unless they have been injured. 

 The sugar beet takes various sub- 

 stances out of the soil water, but :t 

 does not permit the passage of sugar 

 into the soil water. And yet nectar, 

 essentially sugar, is passed out of the 

 plant, within which it was manufac- 

 tured. This is because it is secreted, 

 or excreted, through specialized 

 glands. Everyone who grows plants 

 in a bay window has seen young clo- 

 ver or grass leaves with a drop of 

 water on their tips at some time or 

 other. A few grains of bird seed 'n 

 a flower-pot covered by a pane of 

 glass will show this as quickly as the 

 seedlings come up. 



These drops pass out finally through 

 pores; but they are drops of water 

 and not nectar. If we can imagine a 

 gland behind such a water pore, se- 

 creting sugar— letting it really get 

 out of the cells with or into the 

 water — we can picture a nectar gland. 

 Such glands occur in some flowers. 

 Some botanists believe that extra- 

 nuptial nectar glands were originally 

 water glands that have acquired the 

 habit of secreting sugar. 



This habit is a very unusual and a 

 very peculiar one. It is not readily 

 understood except as it may be con- 

 nected with usefulness to the plant. 

 If this usefulness is not indirect, in 

 the ways suggested by Darwin and 

 Belt, or otherwise, it must be direct. 

 Water glands relieve over-pressure 

 when absorption is high and evapora- 

 tion low; in some of the calla family 

 the water even spurts from the tips 

 of the leaves at times. But sugar is 

 not like water, taken in in quantity 

 and to spare; it is manufactured, an.i 

 in the case of nectar glands it is 

 manufactured where it is secreted. 

 Nobody has yet suggested any physi- 

 ological function of plants calling for 

 sugar safety-valves situated in the 

 queer positions occupied by extra- 

 nuptial nectar glands; and no satis- 

 factory direct physiological explana- 

 tion of the nuptial glands has been 

 s-iggested. 



The actual status of nectar in 

 botanical science is about this: when 

 it is produced in flowers, and in som» 

 cases when it is outside of them but 

 near them, if demonstrably serves to 

 secure cross-pollination through the 

 aid of insects, or humming birds and 

 their like, when the flowers are long, 

 tubular and red, as in the trumpet 

 creeper, the trumpet honeysuckle and 

 the scarlet salvia. It is then "nuptir.l 

 nectar." When it does not serve the 

 plant in this way, and so is "extra- 

 nuptial," it occurs in the neighbor- 

 hood of the flowers, as in cotton, 

 sweet potato, trumpet creeper and 

 paeony, where it attracts numbers of 

 ants, which are often very pugna- 

 cious ,and to the extent of their ac- 

 tivities it prevents injury to the es- 

 sential flower buds and flowers, es- 

 pecially in their early stages; or it 

 occurs on developing leaves during 



