STRUCTURE AND PHYSIOLOGY OF THE PLANT 



barberry ; 



edge of the position of the fruit-buds, in order that such buds may be saved or thinned, as the case may 

 require. Merely to cut off limbs does not constitute pruning. 



A leaf may comprise three parts, — the expanded part or blade ; the stalk or petiole ; appendages at 

 or near the base of the petiole, known as stipules. These parts are shown in Pig. 12. Very many kinds 

 of leaves bear no stipules. Many leaves also lack petioles or are sessile. The blade of the 

 leaf is distinguished in form by comparing it with geometrical figures, as circular, rhom- 

 boidal, ovate, oblong, linear ; or with familiar objects, as kidney-form or reniform, heart- 

 shaped, lanceolate or lance-form, needle-shaped. The margins are distinguished as serrate 

 or saw-toothed, dentate or toothed, sinuate or wavy, or as entire ; and many other techni- 

 cal terms are used in descriptive works to distinguish leaves, in order to identify the species 

 to which they belong. The leaf-blade may be of one piece, when it is said to be simple ; or 

 of two or more separate pieces, when it is said to be compound (Fig. 13). Leaves are com- 

 mon sources of food for domestic animals, forming a good part of the substance in hay and 

 forage ; they also aiford human food in lettuce, rhubarb (petioles), celery (mostly petioles), 

 salads and "greens." 



All plant organs are usually explained in terms of roots, 

 stems or leaves, — that is to say, the other organs are supposed to 

 be derived from one or the other of these three types. Thorns 

 and spines are branches (stems) in the hawthorns ; leaves in the 

 stipules in the common locust ; outgrowths of the stem in common 

 briars and many desert plants. Climbing organs are roots in the English ivy, 

 trumpet creeper and poison ivy ; main stems in hop and morning-glory ; 

 branches in the grape and Virginia creeper; leaf-blades in peas; petioles in 

 some species of clematis; probably stipules in some kinds of smilax. 



Flowers are supposed to be historically derived from leaves, as explained 

 in the succeeding article. The parts of a flower may be in as many as four 

 series (Pig. 14), — the calyx or outer part, usually most like the foliage leaves ; 

 the corolla, usually the showy part ; the stamens or pollen-bearers ; the pistils 



or seed-bearers. If the calyx has separate leaves, they are called sepals ; if the Rg. g. Flowers of peach, one 

 corolla has separate leaves, they are called petals. The f™"" each bud. 



end of the stem on which the flower sits is called the receptacle or torus. All these 

 parts are explained in Pigs. 14, 15, 16, 17, 18, 40. Often, numbers of flowers are 

 combined into one group or cluster ; sometimes the cluster is so dense and definite 

 as to appeal to the non-botanist as one flower, as in all the composites, of which 

 ^ .„ ^ ^ . / 1<^^: the sunflowers and asters and goldenrods and thistles are examples (Pig. 16). 

 wf^^m ^Bt Sometimes the cluster is less definite and yet compact enough to make a single 

 V Jr ^B impression, as in the clovers. .Dried flowers form part of the substance of hay and 

 forage. Flowers or flower parts or heads are sometimes eaten by man, as in the 

 true artichoke, and also in cauliflower and pineapple in which the edible part is 

 made up of a mass of thickened stem and flowers. 



The fruit, in technical and botanical usage, is the ripened peri- 

 carp (or ovary) and all the parts that are coalesced with it. In the 

 agricultural plants, the pericarp may or may not be wholly free 

 of adjacent parts. It is free in the cereal grains, and also the pod-fruits of the legumes , 

 (peas and beans and all their kin), the fruits of the orange kind, of tomatoes and pep- 

 pers, the stone-fruits, and cotton, and the banana. The apple and pear are carpels (a 

 compound pistil) imbedded in a thickened stem, the carpels forming the core. Melons,, 

 pumpkins and squashes are of similar morphology, — the turban squashes show the struc- 

 ture. The strawberry has many fruits imbedded in a pulpy stem or torus. The raspberry 

 is formed of many cohering drupes. The blackberry is formed of cohering drupes 

 attached to a specialized torus or stem. The fig is a hollow torus or stem with many 

 fruits on the inside ; it may be likened to a strawberry turned inside out. The mulberry 

 is a cluster of ripened fruits ; the bread-fruit is similar. The gooseberries (Fig. 19) are 

 ripened ovaries, the dried flower-parts remaining attached. Currants are similar, but 

 the flower-parts usually drop early. Some fruits, as the chestnut (Fig. 20) and walnut, 

 are contained in burs or husks that are no part of the fruit itself. 



Fig. 10. A spur of 

 apple, showing the 

 leaves and flowers 

 that came from the 

 terminal fruit-bud. 



Fig. 11. 

 Cluster of fruit- 

 buds of sweet 

 cherry, with one 

 pointed leaf-bud 

 in center. 



