100 



CASSELL'S POPULAE GAEDEXIXG. 



soil may be altered in character, taken up and 

 utilised ioj the plant. The phenomena also show 

 very remarkably the interdependence of living or- 

 ganisms of various natures one upon another, and 

 upon mineral matters, and they give some hint of 

 the changes and activity going on in that soil which 

 the generality of people still look: on more especially, 

 but very erroneously, as an illustration of fixity and 

 repose. 



Solvent Action of the Roots. — Another means 

 by which insoluble matters in the soil become 

 taken up by the plant is explained by the solvent 

 action exercised by the roots themselves. The 

 tips of the roots above the root-cap, or the extreme 

 ends of the root-hairs, come into close contact with 

 the particles of soil, and then 

 an acid exudation from the 

 cell takes place, which imme- 

 diately attacks the particles 

 of soil, and aided by the water 

 around it, effects the solution 

 of the mineral matter which 

 it contains. The solution is 

 absorbed as fast as it is pro- 

 duced, and so none is per- 

 ceptible in the soil itself. It 

 is, however, to be noticed that 

 this acid exudation from the 

 cell- wall is produced as a 

 consequence of direct contact 

 with smtable matter, but not 

 otherwise, just as the gastric juice in the stomach of 

 an animal is only produced when the glands which 

 secrete it are directly stimulated by the presence 

 of food. 



Summary. — So far then as we know at present, 

 liquid food, or rather liquid materials capable of 

 being converted into food, are introduced into the 

 roots of plants in one or other of three ways — by 

 direct osmotic absorption or diffusion, as in the case 

 of water and substances dissolved in it ; by the agency 

 of "microbes," which turn the insoluble into the 

 soluble ; and by the agency of the roots themselves in 

 furnishing at the right moment, and in the right 

 quantity, a proper solvent. 



The substances introduced into the plant by the 

 roots are, first and foremost, water; then mineral 

 matters, of which potash and phosphates are among 

 the most important, and nitrates, which supply the 

 nitrogen that is a constant component element of 

 protoplasm, and hence illustrates the reason why 

 nitrogenous manures, such as guano, nitrate of 

 soda, or ammonia- salts, are so valuable in promoting 

 vegetation. 



COMMON GAEDEN FLOWEES. 



The Common Rock Rose. — This weU-known 



British and European -plant is JSeJianthemum vtilgare, 

 the name being derived from the Greek helios, the 

 sun; and anthemon, a flower. Vulgat-e mesins com- 

 mon, and refers to the prevalence of the plant. It 

 is also known as the Sun Eose, the Little Sunflower, 

 and the Dwarf Cistus. Linnseus named it Cistus 

 hdianthcmum. It is to be found in plenty in dry and 

 hilly pastures, or in chalky or gravelly soil. There 

 are several species which were introduced from dif- 

 ferent parts of Europe, and one, at least, from Xorth 

 America ; but the fine varieties which are now found 

 in cultivation are really very handsome and show^' 

 plants, wliich are probably seedlings from H. rulc/are, 

 though some are imagined to 

 be distinct species. They are 

 well termed a beautiful class 

 of pereimials, and they are 

 excellent for rough rock- 

 woik, where they can take 

 root between the stones ; also 

 for banks, edgings, &:c.. in hot 

 and exposed situations ; they 

 appear to thrive on any soil, 

 but show to the greatest ad- 

 vantage on a chalky one ; 

 the flowers are rather tran- 

 sient, but produced in such 

 quantities and so continu- 

 ously, that tufts are covered 

 viith. blossom for a considerable period of the year. 

 The close, compact, trailing growth particularly fits 

 them for planting near ledges, where they can hang 

 down over the front, as in the case of rock-work. 

 Certain varieties can be increased in the readiest 

 manner by dividing the roots in the autumn and 

 spring, or by saving seed and sowing it in the open 

 groxmd. 



There are a few double varieties that produce large 

 full flowers of a very showy character, viz., the rosy- 

 buff, chocolate, sulphur, and yellow. Of single 

 varieties, the following are well deserving atten- 

 tion : — 



Cecilia, straw and yellow. Oculata. 

 Garibaldi. Sudbui-y Gem, ricli rose. 



Lady Elizabeth. Tigrinum florepleno. 



Magniflcent, primrose and Yellow Beauty, 

 orange. J 



Lychnis. — This genus comprehends a rather nu- 

 merous group of hardy herbaceous perennials, a few 

 of which are very handsome border plants. The name 

 Lychnis — from hjchnos, a lamp — refers to the bril- 

 liancy of the flowers. One of the best known is 

 Lychnis chalcedonica ; this is a well-known old border 

 plant, gi-owing two feet or so in height, and bearing 



EocK Eose. 



