SC I E N C E -Supplement. 



FRIDAY, MAY 14, 1886. 



CROSS-FERTILIZATION OF PLANTS BY 

 BIRDS. 



Adaptations for cross-fertilization exist in an 

 almost endless variety throughout the vegetable 

 kingdom, and have afforded a wide field for study 

 and speculation to biologists. Many of great in- 

 terest have been described by Hermann Miiller as 

 occurring in South American plants ; and now 

 the well-known South American naturalist, Fritz 

 Miiller, adds in Kosmos (1886, i. 93-98) a very re- 

 markable discovery of adaptation to cross-fertiliza- 

 tion by birds, — the first case of the kind, it is 

 believed, that has been observed in the vegetable 

 kingdom. 



The flowers of the common European myrtle, 

 "with their delicate white corolla and crown of 

 white stamens and simple pistil, are familiar to 

 all. Very similar are the white flowers of the 

 trees and shrubs belonging to the numerous species 

 of the genera Campomanesia, Psidium, Myrcia, 

 and Eugenia of the same family (Myrtaceae), oc- 

 curring in great abundance in South America. 

 Many of the species blossom in such profusion 

 that the trees appear nearly white, and the pleas- 

 ant odor that not a few give off attract bees and 

 other insects in great numbers ; and while in many 

 others the flowers are not so conspicuous, and the 

 perfumes not so evident, yet the pollen is easily 

 transferred from flower to flower, and tree to 

 tree, by the agency of insects. 



In this uniformity among the genera and species 

 a singular exception is found in the ' goiabo do 

 campo,' — a not uncommon tree in the higher 

 lands of Brazil, and widely known for its excel- 

 lent fruit. The single species belong to the genus 

 Feijoa ; and its popular name, as well as its mode 

 of growth and its foliage, recalls the wide-spread 

 common guava-tree (Psidium pomiferum). 



The flowers are found usually at the extremity 

 of the twigs, or more rarely in the axils of the 

 leaves, in groups of from two to five, on short 

 stems. The leaves in whose axils the flower- 

 stems, or the twigs bearing them, occur, are re- 

 duced to rudimentary bracts ; and the flowers, 

 for this reason, are more conspicuous than they 

 would be were they enveloped by leaves, as is 

 usual in the allied genera. A yet more especial 

 adaptation to the means by which they are ferti- 



lized is the duration of flowering, which extends 

 for months, during the entire spring, single blos- 

 soms appearing here and there over the tree. 



The sepals form two pairs, — those of the one 

 about six millimetres in length, and of equal 

 breadth ; of the other, twice as long and a little 

 wider. In the unfolding of the blossom they are 

 turned downwards, and present only the dark 

 reddish-brown inner side. The petals at first are 



BLOSSOMS OP FEIJOA, FIVE EIGHTHS NATURAL SIZE. 



about fifteen millimetres long and as many broad, 

 firm and leathery, and arched outwards : the in- 

 ner side, of a purplish-red color. Within a day 

 they grow to double the length and breadth, and 

 so roll up longitudinally that they form a tube not 

 more than one-third of the width, the leaves of 

 the two pairs rolling or turning in opposite direc- 

 tions. 



Together with these changes in size and shape, 

 there are others in color and taste. The external 

 side of the petal, all that is now visible, becomes 

 pure white, contrasting with the dark background 

 of the sepals ; and instead of being thickened 

 and tasteless, or with a slight acrid taste, as is 

 usual in so many of its congeners, like the clove 

 and other species, it has now become soft and 

 very sweet, and without any acridity. 



The dark blood-red stamens, to the number of 

 about fifty or sixty, are about eighteen millimetres 

 in length, thickened and stiff, and expanding 

 above into a crown more than an inch in diame- 

 ter. The anthers lie horizontally, and liberate 

 their bright yellow pollen nearly at the same time 

 that the petals reach their complete development. 

 The single pistil is likewise firm and stout, and 

 extends above the plane of the anthers. As an 

 unusual occurrence, there were found at one time 



