Commercial Gardening 



shoots for the purpose of assimilation. These shoots are flat and leaf- 

 like, but it will be noticed that they bear flowers near the centre, a thing 

 no true leaf does. It will also be noticed that instead of spreading out 

 horizontally these peculiar shoots (known botanically as cladodes or phyllo- 

 clades) are set more or less vertically. Other plants with modified struc- 

 tures are to be found in such genera as Asparagus, Acacia, Eucalyptus, 

 Grevillea, Phyllanthus, Phyllocactus, Phyllocladus, Semele, &c. [J. F.] 



6. LEAVES AND THEIR WORK 



Seed Leaves and True Leaves. The first leaves of a plant are those 

 formed in the seed, and which may or may not rise above-ground during 

 germination. Those of the Cabbage, Mustard (fig. 13), Gourd (fig. 18), 



Beech, and Onion rise above-ground 

 and become green. As soon as this 

 has taken place the seedling has 

 started life on its own account, 

 manufacturing its own food in the 

 green seed leaves and stem. The 

 seed leaves of many plants become 

 fleshy, store food while in the grow- 

 ing seed, and never rise above-ground 

 during or after germination, but 

 supply food to the seedling till able 

 to forage for itself. Examples of 



Fig. 29.-Vertical section through Leaf of Frawiscea fafe may be geen J n the gar( ] en 

 eximia, showing Epidermal, Palisade, and Spong n en TI t*^ x ft 



Tissue, and two stomata cut through Pea, Sweet Pea, Broad Bean, Scarlet 



Runner, Horse-chestnut, and Oak 

 The seed leaves differ more or less widely in form 

 All of the plants mentioned in this 

 paragraph, except one, have two seed leaves or cotyledons and belong 

 to the class Dicotyledons. The Onion, Lily, and others have only one 

 cotyledon, and are Monocotyledons. The seed leaves of Iris and grasses 

 never rise above-ground, and as they have only one each they belong to 

 the latter class. 



The true or rough leaves are those that follow the seed leaves in 

 succession, increasing in size and varying in form with each individual 

 till the plant reaches the adult state. The leaves, taken altogether, con- 

 stitute the foliage of the plant. 



Structure and Contents of a Leaf. The naked-eye characters of a 

 leaf may be seen in that of a Vine. The leaf is three- to five-lobed, 

 with as many primary veins running from the base to the tip of each 

 lobe. Smaller veins pass through the leaf in a variety of directions, the 

 smaller ones forming a kind of netting. The veins are fibro- vascular 

 tissue that come from the stem, pass through the leaf stalk, and divide 



(fig. 19, p. 35). 



from the true leaves that follow. 



