BOTANICAL CHARACTERS 



69 



tissues (Fig. 14). The tissues of such plants become differ- CHAP, 

 entiated into groups, forming organs which have different duties ' 



to perform. Of these organs the most important are the root, 

 stem, and leaf which are connected with nutrition and growth, 

 and the flower which contains the reproductive organs of 

 the plant. The life -cycle of the maize plant begins with the 

 fertilization of the egg-cell in the ovule by the male germ 

 cell, as described in IT 78, by which a new plant-being is 

 brought into existence. The new cell, formed bv the union 





A I 



Fig. 13. Fig. 14. 



Fig. 13. — Plant cells, as seen under a high-power microscope, showing 

 strands of protoplasm, nucleus, nucleolus, etc. A, B, young cells ; C, an older 

 cell, from the developing maize root; D, cell from the hair of Tradescantia; 

 E, parenchymatous cell from the cortex of Ranunculus. (From Sir F. Darwin's 

 Elements of Botany, Cambridge University Press.) 



Fig. 14. — Transverse section through a leaf (of hellebore), showing tissues 

 and cells. From above downwards are seen the upper epidermis, the palisade 

 cells, the spongy tissue (in which a vascular bundle is seen), the lower epidermis 

 (in which is shown a single stoma opening into a large intercellular space). 

 Note that the chloroplasts are arranged along the cell walls, especially in the 

 palisade tissue (A). (From Sir F. Darwin's Elements of Botany, Cambridge 

 University Press.) 



of the two germ-cells, develops by cell-growth and repeated 

 cell-division (somatic division) into a seed. 



62. The Seed. — The seed consists of an embryo plant and 

 a mass of reserve food-material known as endosperm, wrapped 

 in two protective seed-coats, the outer or testa and the inner 

 or tegmen. In the case of maize and other grasses, the seed 

 is further surrounded by the pericarp or envelope of the grain 



