INTRODUCTIOX. 5 



possessing the special functions of conducting and storing 

 the constituents of elaborated sap). 



There are, moreover, certain isolated tissues* in plants, such 

 as glands and resin-canals, which have special functions, and these 

 will be examined in due course (Chap. vi.). 



In lower plants, such as the Alg£e, all functions, — viz., assimila- 

 tion, respiration, nutrition as a whole, and reproduction — may 

 be carried on in the one or perhaps the few cells of which the plant 

 is made up ; and thus, the division of labour which obtains in a 

 plant composed of many tissues, is absent in the lower forms. 



In higher plants the function of reproducing the species is 

 relegated to well-marked special organs, and the processes occur- 

 ring in these will be examined in detail in Chapter ix. ; certain 

 well-defined types being selected for this purpose. 



In Chapter vii. ; the phenomena involved in the production of 

 fresh cells from pre-existing ones (cell-division) will be gone 

 into, and, finally, in Chapter x. the physiology and chemistry of 

 the cell will be considered. 



An outline of the main groups and subdivisions into which 

 the vegetable kingdom is divided will be found of use for 

 purposes of reference, although it is not here intended to deal 

 with botany from the point of view of classification. 



Such an outline as the following will indicate the main genea- 

 logical relationships of members of the plant kingdom : — 



* N(jt isolated in the strict sense of the term (see Chap. vi. ). 



