LECTURE I. 



presence of light as the Almond-tree : it consists, in the first place, of a cylindrical 

 part {{) tending upwards, which we recognise immediately as the future main stem of 

 the young Almond-tree, and at the upper portion of which the young leaves {b) are 

 already visible. The two bodies, densely filled with nutritive matters marked {c) in 

 our figure (the Cotyledons), are also to be regarded as leaves which spring from the 

 seedling stem. We comprehend the whole of this structure under the name of Shoot, 

 as opposed to Root, and distinguish on it two categories of parts, viz. the leaves 

 {b and c), and the Shoot-axis (z). However sharply the leaves are here and in other 

 cases separated off from the shoot-axis, an extended comparison of different forms of 

 plants leaves no doubt that they are nothing -but portions or outgrowths of the shoot- 

 axis, and must be taken together with this as 

 one whole. Our plant is thus in the first 

 instance segmented into root and shoot, as 

 the two chief forms of vegetative organs. 



If, in contradistinction to this highly organ- 

 ised seedling, which developes into a tree, we 

 now contemplate a small plant of extremely 

 simple nature, growing even without cell divi- 

 sions, as Boirydium (Fig. 2), we here again 

 find the two parts. Root and Shoot. The 

 first, consisting of thin, branched tubes, has 

 penetrated into the substratum (wet clay), it 

 fixes the entire plant, and at the same time 

 absorbs mineral nutritive materials from the 

 soil, and it does both by virtue of a series of 

 properties which it shares with the highly organ- 

 ised root of the Almond plant ; it is only by the 

 external form and visible internal structure 

 that it is distinguished from it; the function, 

 performed in virtue of special irritability, is in 

 all essential points the same in both. The 

 other portion of our Botrydium plant is a 

 globular swelling of the vesicle of which the 

 whole plant consists: this part, however, 

 comes forth above the substratum, and meet- 

 ing the light, the usual green colouring matter of plants is produced— viz., chlo- 

 rophyll; by means of this, it is enabled to decompose carbon dioxide, and, with the 

 aid of the mineral substances absorbed by the roots, to produce organised plant- 

 substance. In this point the globular shoot, in spite of its extremely simple, 

 orgamsation, corresponds to the highly developed germinal shoot of the Almond 

 It does so also in a second point; the reproductive organs arise in it sooner or later, 

 though m a much simpler form than is the case with the Almond-tree, on which the 

 reproductive bodies (oospheres and pollen-grains), also microscopically small, only 

 arise after some years-when the germinal shoot is strongly developed and much 

 branched— m the mterior of the flowers, which are simply altered shoots. A detailed 

 exposition of these matters would present a thousand examples, which, even on 



FIG. 2. — Botrydtutn g^'anulainm. An Alga, mag. 

 nified about 30 times, w root; s green shoot (after 

 Rostafinski). 



