MORPHOLOGY 11 



root, and they are typically green expanded surfaces 

 of different shapes according to the species. 



The three fundamental elements roots, stems, and 

 leaves are all that compose the vegetative plant, 

 which, under favourable conditions of nutriment, may 

 continue to grow for a long time. Some of the very 

 large Monocotyledons, for instance, live the whole of 

 their long lives as vegetative plants, and then at the 

 end of a lifetime produce a great number of reproductive 

 organs and die. 



The fourth set of organs the reproductive are 

 known in their simplest terms as Sporangia. The 

 " flowers " which we associate with most of our common 

 plants are composed of the essential sporangia and 

 a number of modified leaves, which form altogether 

 structures of extraordinary complexity and variety. 

 In many cases the colours, designs, and positions of the 

 modified leaves which form the flower have a very 

 definite relation to the insects which visit it and do an 

 important work in carrying the pollen which is produced 

 in the sporangia (pollen sacs) from one flower to another. 

 But this will lead us to another aspect of the subject. 

 Let us for a moment consider the four essential elements 

 of the plant's body. 



The Roots generally ramify in the soil and live alto- 

 gether underground ; this is, however, a physiological 

 rather than a morphological character. Morphologi- 

 cally the principal difference between roots and stems 

 is that, though the roots and the leaves both spring 

 from the stems, the roots themselves do not bear leaves. 

 Some plants have underground stems, which are often 

 extremely like roots in their external appearance, 

 but on them one can generally find traces of the re- 

 duced leaves in the form of small brown scales, which 



