NATURAL HISTORY NINETEENTH CENTURY. 645 



little advance as compared with systematic botany. What had been 

 done for the former was chiefly due to the labour of Grew, Malphigi, 

 and Hales. In 1815 TREVIRANUS drew attention to the development 

 of the vegetable embryo; and in 1823 AMICI discovered the fertiliza- 

 tion of the ovule by the pollen-tubes. This subject has since occupied 

 a host of observers ; the processes of cell-formation (cystogenesis) has 

 been perseveringly studied, especially by French and German micro- 

 scopists such as SCHLEIDEN, SCHWANN, MOHL. About 1790 Goethe, 

 seeking to satisfy the scientific spirit which in the contemplation of 

 endless diversity crave:, to discover unity, clearly enunciated in his 

 " Metamorphosis of Plants " a law which, although it attracted little 

 attention at the time, was found afterwards to be a new light for the 

 botanist. It declares that the various parts of plants, calyx, corolla, 

 stamens, pistils, etc., are in reality but leaves modified to adapt them 

 to particular functions. It is meant not that these organs individually 

 were at one time leases and were afterwards transformed, but that they 

 are constructed of the same parts and elements as the leaf, and are 

 arranged upon the same plan. In other words, the leaf is taken as 

 the type of all vegetable organs. The similarity of sepals and petals 

 to leaves is often sufficiently obvious, and by careful examination is 

 traceable in all cases ; and the community of nature in petals and 

 stamens is proved by the instances in which the same parts of a plant 

 are developed, sometimes into petals and sometimes into stamens. 



In 1875 Mr. Darwin published, under the title "Insectivorous 

 Plants," an account of his examination of certain plants which have 

 the singular habit of capturing insects. The subjects of observation 

 were species of Drosera (Sundew), Dioncea muscipula (Venus's Fly- 

 trap), Pinguicula, etc., and the most remarkable result of the investi- 

 gation was that these plants derive their nutriment from the bodies of 

 the insects they entrap. Some of them actually digest the insects by 

 a process analogous to that which occurs in the stomach of an animal. 

 Observations of similar habits have also been made by Sir Joseph 

 Hooker on other classes of plants, and will doubtless be extended. 

 The Dioncea muscipula mentioned above is one of the most wonderful 

 plants in the world, from the rapidity and force of the movements by 

 which the insects are caught. The lightest touch affecting any one of 

 three or four minute filaments which project from the face of the leaf, 

 suffices to make the lobes immediately close, their margins turning 

 inwards. The mechanism of this movement, which is so like that of 

 an animal, has not yet been made out. It is singular that chloroform 

 and other anaesthetics have a certain effect on these plants. Another 

 of Mr. Darwin's works which should be noticed here is the " Ferti- 

 lization of Orchids," published in 1862, in which he points out wonder- 

 ful relations between insects and flowers, which strongly support his 

 Theory of Natural Selection, and explain many particulars of both 

 insect and plant organization hitherto without meaning. 



