PLANTIGRADES 



PLANTS 



221 



temperature in their contents. These beds are 

 usually provided with hot-water pipes, tanks, or 

 flues lielow, for the purpose of giving bottom heat 

 when required. 



See also FORCING, GARDENING, HOTBED, ORCHIDS, 

 PEACH, VINE, &c. ; S. Wood, Forcing Gardening (1881) ; 

 Fawkes, Horticultural Buildingi ( new ed. 1886 ) ; Rivers, 

 The Orchard House ( 1881 ) ; and other works by Baines 

 <1885), Hibberd (newed. 1880), May(newei 1888), and 

 Williams (new ed. 1883). 



Plantigrades. See BEAR, CARNIVORA. 



Plailtin. CHRISTOPHE, an eminent printer, 

 was born at St Avertins near Tours, in 1514, and 

 settled as a bookbinder at Antwerp in 1549 ; some 

 six years later he began to print. The books that 

 came from his office are distinguished for their 

 accuracy and beautiful workmanship and finish. 

 His business prospered, and he had often twenty 

 presses or more in active operation at once. The 

 most noted of all his publications is the Biblia 

 Polyglotta (8 vols. 1569-73), which was printed 

 under the personal superintendence of Arias Mon- 

 tiiniis, the court chaplain of Philip II. of Spain. 

 Plantin's editions of the Bible in Latin, Hebrew, 

 and Dutch, and editions of the Greek and Latin 

 classics, are scarcely less celebrated. He died at 

 Antwerp, 1st July 1589. He had set up printing- 

 establishments in Leyden and Paris, and these, 

 with that in Antwerp, were carried on by the 

 husbands of his daughters. His office in Antwerp 

 remained in the possession of the family of John 

 Moretus, his son-in-law, until it was bought by the 

 city in 1876 for 1,200,000 francs; out of it was 

 created the ' Musee Plantin ' ( 1877). 



See Life by Max Kooaes (in French, Antwerp, 1882) ; 

 Backer and Kuelenn, Annalet de Flmprimerie Plan- 

 tinirnnt (Brussels, 1865); Uegeorge, La, Maison Plantin 

 { 3d ed. Paris, 1886 ) ; and Correspondanee de Plantin 

 (edited by Kooses, Ghent, 2 voU. 1884-86). 



Plant-lice. See APHIDES. 



Plants. It is not possible to frame a complete 

 definition of a plant as opposed to an animal ; the 

 most obvious distinction is that a plant is fixed, 

 while an animal moves ; and though it is quite true 

 that plants form that kingdom of nature which is 

 characteristically passive in ita life, while the animal 

 life is more vigorous, yet there are many animals, 

 such as a sea-anemone, which are as fixed as a plant; 

 and all plants are sensitive to the sun's rays, and 

 move in response. Nor can we make a formal 

 distinction lietween them in terms of the food they 

 require ; for although it is true that plants live 

 upon simple unorganised materials, the salts ami 

 water of the soil, and the carbonic acid and oxygen 

 of the air, and indeed serve as the source of all 

 fowl for animals, yet there are many parasitic 

 plants which live on the juices of other living crea- 

 tures. What chiefly maxes such a definition im- 

 possible is that at the bottom of the ladder of 

 life there are innumerable living creatures which 

 it is a mere formality to call either plants or 

 animals. From such creatures as these it is possible 

 that the two great kingdoms of nature have been 

 evolved step by step in constantly diverging linos. 

 Hut the diversity of nature of plant and animal 

 life is such that they are mutually helpful to each 

 other ; plants having the means of feeding upon 

 the carlionic acid of the air, using the carbon and 

 giving out the oxygen, thus forming matter for the 

 life of animals, who in return, by breathing out 

 carlionic acid, help to keep the air in a fit state for 

 plants. This mutual relation of the two kingdoms 

 finds another expression in the aid that insects 

 and some bird** give to the higher plants, for in 

 tliir (wjirch for honey they become covered with 

 ]>ollen, and carrying it from flower to flower secure 

 croHx-fertilisatioii ; while it is probable that the 



bright colours of flowers have been to a certain 

 extent evolved by the natural selection which the 

 insects who visited them have exerted, by going 

 more often to those of the brighter colour. 



For the classification of plants and list of allied sub- 

 jects, see BOTANY ; for their life-processes, see VEQB- 

 TABLE PHYSIOLOGY ; see also the articles AGRICULTURE, 

 BIOLOGY, CULTIVATED PLANTS, FIBROUS SUBSTANCES, 

 FLOWEH, GARDENING, and those on the great groups of 

 plants ALG.S, CONIFERS, CYCADS, FKENS, FUNGI, &c, 



MOVEMENTS OF PLANTS. The movements of 

 plants may be divided into ( 1 ) those that take 

 place during growth, including growth itself, 

 many of which are common to an plants ; and (2) 

 those that may be seen in mature plants these are 

 rather the exception than the rule. The whole 

 matter is fully treated in the article on Vegetable 

 Physiology (q.v.); here a short and general account 

 will be given. 



Growth, in its rate and direction the direction 

 being really determined by the relative rate of 

 various parts is influenced by many factors ; the 

 effects of temperature, light, gravitation, and mois- 

 ture are well marked. 



Temperature. There is a certain temperature 

 at which growth is most rapid, also a minimum 

 and a maximum at which it ceases ; these points 

 are different for different plants. 



Light. The formation of chlorophyll and there- 

 fore of starch depends, in nearly all cases, upon 

 light, but that light generally retards growth may 

 l>e seen by the long stems of plants grown in the 

 dark, and by the bending of plants grown in a 

 window towards the light. In a few cases, as in 

 the older parts of the stems of ivy, growing parts 

 turn away from the light. The rays towards the 

 blue end of the spectrum are the most powerful 

 in their effect upon the direction of growth. 



Gramtation. Stems gsnerally grow upwards and 

 roots downwards ; that this is an etl'ect of gravita- 

 tion is proved by the following experiments. Place 

 a seedling in a horizontal position ; the growing tip 

 of the stem will turn upwards and that of the root 

 downwards. Rotate a plant slowly in a vertical 

 plane, so as to cause the direction of gravitation 

 to alter constantly ; the direction of the growth of 

 stem and root is irregular. Rotate a plant very 

 rapidly, so as to introduce the so-called centrifugal 

 force ; the stem will grow towards the centre, that 

 is, in the direction opposite to that of the acting 

 force, and the root away from it, that is, in the 

 direction of the acting force. 



Moisture. Roots always grow in the direction of 

 the greatest moisture. This effect is a stronger 

 one than that of gravitation, for if seeds germinate 

 in a sieve filled with damp sawdust the roots at 

 first grow downwards until they have grown 

 through the sawdust out into the dry air ; then the 

 direction of growth changes, and the tips bend 

 round and grow up again into the damp sawdust. 



'Spontaneous' Movements of Growing Plants. 

 There are other movements of growing parts the 

 causes of which are not well understood. Thus, 

 the leaves of a young liud are kept close together, 

 l>ent over the tip of the stem, by the more rapid 

 growth of their under than of their upper surfaces. 

 When the bud is older the upper surfaces of the 

 leaves begin to grow more quickly than the under 

 surfaces and the leaves unfold. Such movements 

 are spoken of as nutations. The tips of climbing 

 stems describe a ' circumnutation ' due to successive 

 alterations in the rate of growth of the sides of the 

 stem. It is in virtue of these movements that such 

 plants are able to climb by twining round a sup- 

 port. Tendrils have similar movements, but there 

 are further complications (see VEGETABLE PHYSI- 

 OLOOV). All these movements are due to unequal 

 growth of the parts of the plants. 



