WHAT IS A PLANT? 79 



in Afitheaj the common green anemone ; in Bonellia^ one of the 

 Spoon-worms (Gephyrea) ; and as high up as Crustacea, in Idotea, 

 a member of the Isopoda, or the wood-louse order.* 



Chlorophyll, like starch, is absent in the Fungi. No less is it 

 absent in many higher plants, when parasitic, as in Broom-rape, 

 Fir-rape y and some Orchids. 



However, although its presence fails as a diagnostic feature of 

 plants, we may take that presence as a pretty safe indication that 

 the organism possessing it is a plant. 



V. — Function of Locomotion. For many years this was 

 held to be peculiar to animals alone. Cuvier himself, in 1828, f 

 speaks of " animated beings " possessing sense and motion, 

 and " inanimated beings " possessing neither, but simply " vege- 

 tating" — a term, by the way, not wholly misapplied to many 

 members of the genus " Homo " in our own time. But the rapid 

 progress of science during the last fifty years has done away 

 with motile power as a distinctively animal function. True, the 

 upward or downward movement of stem or root, and the various 

 motions of leaves and other organs of certain plants cannot be 

 said to be voluntary ; but there are many cases of movement in 

 plant-life that have their counterpart among animals, and that 

 place the existence of this function among plants beyond scep- 

 ticism. 



Upon this power of movement in plants, Cuvier, as we shall 

 presently see, founded his first great distinction between them and 

 animals. His argument breaks down, however, in this its first 

 link. We note four kinds of movement seen in plants : — 



I. — We see in the protopias?n of many of the lower forms of 

 Algce the phenomenon of " rhythmical pulsation " — {i.e., periodic 

 movement of certain spaces called the " contractile vacuoles " ) — 

 which is characteristic of Amoeba and other animals. 



2. — There is motion, undoubted and regular, of the granular 

 contents of cells in many plants. For example, in the Stoneworts 

 (Characae), first noted by Corti ; in Stratiotes, the water-soldier ; 

 in Anacharis (the American water-weed, which is the pest of our 

 canals and ditches) ; in the well-known Vallis7ieria j in the hairs 



* Vide note at end of Part II. of this paper, 

 t " Rfegne Animal," 2nd ed. 



