VERNATION 37 



Oak and Willow, etc. As the distance between any two leaves is two- 

 fifths of the circumference of the stem, the five-ranked arrangement is 

 expressed by the fraction 2/5. In the eight-ranked arrangement the 

 ninth leaf stands over the first, and three turns are required to reach it, 

 hence the fraction 3/8 expresses it. Of the series of fractions thus ob- 

 tained, the numerator represents the number of turns to complete a 

 cycle, or to reach the leaf which is directly over the first; the denomi- 

 nator, the number of perpendicular rows on the stem, or the number 

 of leaves, counting along the spiral, from any one to the one directly 

 above it. 



Vernation. — Prefoliation or Vernation relates to the way in 

 which leaves are disposed in the bud. A study of the individual leaf 

 enables us to distinguish the following forms. When the apex is bent 

 inward toward the base, as in the leaf of the Tulip Tree, it is said to be 

 INPLEXED or RECLiNATE VERNATION; if doubled On the midrib so that- 

 the two sides are brought together as in the oak, it is conduplicate ; 

 when rolled inward from one margin to the other, as in the Wild 

 Cherry, it is convolute; when rolled from apex to base, as in Ferns, it 

 is circinate; when folded or plaited, like a fan, it is plicate; if rolled 

 inward from each margin, as the leaf of the common Violet, involute ; 

 when rolled outward from each margin as Rumex, revolute. The inner 

 surface is always that which will form the upper surface when expanded. 



Inflorescence or Anthotaxy. — A typical flower consists of four whorls 

 of leaves modified for the purpose of reproduction, and compactly placed 

 on a stem. The term Inflorescence, Anthotaxy, is applied to the arrange- 

 ment of the flowers and their position on the plant, both of which are 

 governed by the same law which determines the arrangement of leaves. 

 For this reason flower buds are always either terminal or axillary. In 

 either case the bud may develop a solitary flower or a compound in- 

 florescence consisting of several flowers. 



Determinate, cymose, descending, or centrifugal inflorescence 

 is that form in which the flower bud is terminal, and thus determines or 

 completes the growth of the plant. Ex. : Ricinus communis. 



Indeterminate, ascending, or centripetal inflorescence is 

 that form in which the flower buds are axillary, while the terminal bud 

 continues to develop and increase the growth of the plant indefinitely. 

 Ex. : the Geranium. 



Mixed Inflorescence is a combination of the other two forms. 

 Ex. : Horse Chestnut. 



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