QUEEN ANNE'S LACE; THE PAPAW TREE, AND SELF-HEAL 



547 



Ji^HS 



LEAF TERMS 



Plants, sucli as the Iris (Fig. ll.?). present no distinction of 

 petiole and blade, and on section tlieir narrow leaves are ar- 

 ranged as in Fig. 114. In the Pitch Pine (Fig. 118) the three 

 needle-shaped leaves form a fascicle or bundle ; a short sheath 

 surroinids this at its base, furnished by the thin scales of the 

 axillary bud. In the Larch (Fig. 124) the arrangement is much 

 the same, as it is, too, in the Spruce. Such leaves are called 

 awl-shaped. Another kind are the scale-shaped, such as in the 

 Arbor-vitK (Fig. 115), Juniper, and the Cedars. Here the 

 scales which represent the leaves are in great numbers, and they 

 gain the required spread of surface in this way. Petioles that 

 expand and flatten, thus taking the place of the blade, are 

 termed thylladia, such as in soine Acacias (New Holland). 



The stipules present as many variations as the petioles, and 

 their extremes are to be seen in the Pea, the Magnolia, Tulip 

 Tree. In the first they make a conspicuous part of the leaf, 

 while in the beans they are more or less minute. In the Cloves 

 they are united with the base of the leaf-stalk (Fig. 117), while 



It is not at all likely, however, that it has been used in 

 the present horribly destructive war in France. 



When we come to study the leaves of the plants here 

 figured in the cuts, as well as in those in previous arti- 

 cles, or, indeed, in trees and plants in general, it will 

 have to be observed that never more than one leaf springs 

 from the same point on the stem ; but, should two arise 

 from the same joint, they are always situated on oppo- 

 site sides of the stem, the distance of half the circum- 

 ference separating them. If there should be more than 

 two, as in whorls, they are placed equidistant around the 

 joint of the stem, being separated by one-fifth, one- 

 fourth or one-third of the circumference of the stem 

 from each other, depending upon the number of leaves. 

 This assures their being at the greatest possible distance 

 apart, and we never see two or more leaves standing side 

 by side at the same joint, nor are they ever clustered 

 or one above the other. Clustered or fuscicled leaves are 

 shown in Figure 124 of the Leaf Terms to the present 

 article; they represent leaves of an entire branch crowded 



in the Prince's Feather (Polyyoiiuiu oricntalc). Fig. 116, the 

 stipules unite to form a sheath for the stem. The Uyulc corre- 

 sponds to the stipule in some of the grasses, wdiere the sheaths 

 support the blade on their summit, and it occurs on its apex. 

 There are two principal arrangements of leaves on the stem, 

 alternate (Fig. 122) or opposite. When alternate, the single 

 leaves spring, one after the other, from each joint (node) of 

 the stem, and when opposite, there is a pair of leaves at each 

 joint of the stem — one leaf of any of the pairs being exactly 

 opposite its companion on the other side of the stem. When a 

 circle is formed of tliree or more leaves about the joint as in 

 the Bedstraw {.Cralliuiii) , the arrangement is said to be of the 

 whorled or verticillate variety. The rule is unerring which 

 detertnines the place of a leaf upon the stem in the case of any 

 plant ; it appears at its pre-destined point with mathematical 

 accuracy, and the special formula in any case holds true for 

 all species in the vegetable kingdom. Figures 119-123 throw 

 some light on these formuUe. 



into a fascicle. Trees of the Pine family should be 

 closely studied to work out such problems as these. 



Leaves do not make their appearance on trees and 

 plants in a haphazard manner, but spring normally from 

 points which appear on the stem with absolute mathe- 

 matical precision. Their arrangement is uniform for 

 the species, but not the same for other plants. 



From this it is clear that the greatest possible diver- 

 gence is where the second leaf is found on exactly the op- 

 posite side of the stem from the first one, with the third on 

 the side opposite the second, and so on, and consequently 

 over the first one, with the fourth over the second. Two 

 ranks are thus formed, one on one side of the stem and 

 one on the other. This, then, is the two-ranked arrange- 

 ment. By varying the intervals or distances on the spiral 

 line, it is easy to see how we also get a three-ranked 

 arrangement, as well as the most common one of all, the 

 five-ranked. It is very instructive to study these several 

 arrangements on the stems and branches of the plants 

 and trees we can collect. 



Ill Figures 119 and 120 of the Leaf Terms on this 



