CLEMENTATU BOTANY. 



expands, the period of flowering (anthesis) is that which elapses from the first expand- 

 ing of the perianth, till the pistil is set or begins to enlarge, or, when it does not set, 

 until the stamens and pistil wither or fall. After that, the enlarged ovary takes the 

 name of young fruit. 



215. At the close of the season of growth, at the same time as the leaf-buds or seeds 

 are formed containing the germ of future branches or plants, many plants form also, at 

 or near the bud or seed, large deposits, chiefly of starch. In many cases,— such as the 

 tubers of a potato or other root-stock, the scales or thickened base of a bulb, the albu- 

 men or the thick cotyledons of a seed, — this deposit appears to be a store of nutri- 

 ment, whicli is partially absorbed by the young branch or plant during its first stage 

 oi growth, before the roots are sufficiently developed to supply it from without. In 

 some cases, however, such as the fleshy thickening of some stems or peduncles, the 

 pericarps of fruits whicli perish long before germination (the first growth of the seed), 

 neither the use nor the cause of these deposits has as yet been clearly explained. 



§ 4. Functions of the Organs. 



216. The functions of the Root are,— 1. To fix the plant in or to the soil or other 

 substance on which it grows. 2. To absorb nourishment from the soil, water, or air, 

 into which the fibres have penetrated (or from other plants in the case of parasites), 

 and to transmit it rapidly to the stem. The absorption takes places through the 

 young growing extremities of the fibres, and through a peculiar kind of hairs or ab- 

 sorbing organs which are formed at or near those growing extremities. The transmis- 

 sion to the stem is through the tissues of the root itself. The nutriment absorbed 

 consists chiefly of carbonic acid and nitrogen or nitrogenous compounds dissolved in 

 water. 3. I n 80m e cases roots secrete or exude small quantities of matter in a manner 



2V7 lt ^r? pur P 03e not satisfactorily ascertained. 



fjj. The Stem and its branches support the leaves, flowers, and fruit, transmit the 



rude sap, or nutriment absorbed by the roots and mixed with previously organized 



to tl t0 f ^ e leave8 > and retransmit the assimilated or elaborated sap from the leaves 



u (In POwin 6 P arts °f the plant, to be there used up, or to form deposits for future 



th 6 ? i, lhe transi nission of the ascending crude sap appears to take place chiefly 



rough the elongated cells associated with the vascular tissues, passing from one cell 



218 t ty a P rocess but "ttle understood, but known by the name of endosmose. 

 is eh' fl ves are functionally the most active of the organs of vegetation. In them 

 con V I Conducted digestion or Assimilation, a name given to the process which ac- 

 mat? /V he followm g results :— 1. The chemical decomposition of the oxygenated 

 the a- 8ap ' the absor Ption of carbonic acid, and the liberation of pure oxygen at 

 sorh°!d u ary tem perature of the air. 2. A counter-operation by which oxygen is ab- 

 the r \ rom the atmosphere and carbonic acid is exhaled. 3. The transformation of 

 sitionf £ ° f the Cmde 8a P int0 the or g llI1 i zea ' substances which enter into the compo- 

 of l u P lant - The exhalation of oxygen appears to take place under the influence 

 meaT 8nd light ' chiefl y {rom the under surface of the leaf, and to be in some 

 <Wk Ure J egUlatetl b ^ the st omates; the absorption of oxygen goes on always in the 

 fected i'" the da ^ tirae also in certain cases. The transformation of the sap is ef- 

 thp . , Wltlim the tissues of the leaf, and continues probably more or less throughout 



219 % Pa ; t8 of the whole Pi"*- 



are nmH ^ ml ° r g ans seldom contribute to the growth of the plant on whicli they 

 wit), *u ' their functions are wholly concentrated on the formation of the seed 



2 2 o he a ,f n " of a future plant, ' L 



■tamen* j an,h (cul > x and corolla) acts in the first instance in protecting the 

 the ngp tu Pl8tils duri,1 S the early stages of their development. When expanded, 

 they P I° f 1 brilli ant colours which they often display, of the sweet or strong odours 

 in attract' as , not been adequately explained. Perhaps they may have great influence 

 cessarvf u iu8ecls whose concurrence has been shown in many cases to be ne- 



221 T?k due transmission of the pollen from the anther to the stigma, 

 the vn„ Pl8ti1 ' wfa en stimulated by the action of the pollen, forms and nourishes 

 J°«ng seed. The varied and complicated contrivances by which the pollen is con- 



