Flowers 



For classification and identification of trees and 

 other flowering plants, the flowers and fruits, or 

 reproductive organs, are the most important parts. 

 They show the relationships better than the leaves 

 and other vegetative organs, which are less con- 

 stant and often vary greatly under difi'erent en- 

 vironments. Tlie commoner plant families can be 

 recognized by their characteristic flowers. It has 

 seemed desirable, therefore, to describe the flower 

 structure of each tree species in simple terms with 

 measurements. 



The flower is a modified stem bearing four or 

 fewer groups or circles of specialized leaves known 

 as calyx, corolla, .stamens, and pistil (or pistils). 

 The calyx, or outermost group, is composed of re- 

 duced leaves generally green and called sepals, 

 while the corolla consists of larger and usually col- 

 ored parts known as petals. The corolla may be 

 regular with equal petals or irregular with petals 

 of unequal size and may be tuhiilar with the petals 

 united into a tube. The stamens or male organs 

 of the flower have a filament or stalk and an anther 

 or enlarged, usually yellow, part which bears the 

 pollen, or male elements. Sometimes, the stamens 

 may be replaced by staminodes, which are nonfunc- 

 tional or sterile stamens, usually small. 



In the center of the flower there is usually a 

 single pistil or female organ (sometimes few to 

 many) developed from one or moi-e specialized 

 leaves. The pistil consists of three parts: the 

 ovary or enlarged part at the base, the style or 

 stalk above the ovary, and the stigma, the usually 

 enlarged and often sticky end, which receives the 

 pollen. The ovary contains 1 to many ovules, 

 I'ounded whitish female elements. The mature 

 ovary is the fruit, while the ovules become the 

 seeds. 



In position with respect to the other flower parts, 

 the ovary may be superior or infeHor. The su- 

 perior ovary, the common type, is free or separate 

 in the center of the flower and inserted inward 

 from or above the other parts. The inferior ovary 

 is located below the calyx, corolla, and the stamens, 

 which appear to be inserted above. The structure 

 of the ovary, including the number of cavities or 

 cells from 1 to several and number and position of 

 the ovules within, is important in classification of 

 plant families. 



The receptacle is the enlarged base of the flower 

 where the flower parts are inserted. Above the 

 receptacle and inward from the corolla there is 

 sometimes a dish or small part like a circle or ring, 

 often glandular. The receptacle may form a basal 

 tube or cup called the hypanthium. which may 

 enclose the inferior ovary or sometimes surround 

 the superior ovary and bear the other parts 

 located above. 



Though usually possessing stamens and pistil 

 and thus with both sexes or bi-^e.rual. flowers may 

 be of one sex only or unisexual. A ?7iale flower has 

 stamens but no pistil, and a female flower has a 



pistil but no stamens. A species with male and 

 female flowers on the same plant is said to be mo- 

 noecious, while one with male and female flowers 

 on different plants, which are also male or female, 

 is dioecious. In polygamous species flowers of one 

 sex and bisexual flowers are borne on the same 

 individual. 



Fruits 



Developing fi-om mature ovary, the fruit con- 

 tains the seeds and sometimes other flower parts 

 still attached. Present often for longer periods 

 than flowers or also remaining under the trees 

 after falling, the fnaits may be especially helpful 

 in identification. Commonly the fruit originates 

 from a single pistil and is simple. A fruit from 

 several pistils in one flower is aggregate (for ex- 

 ample, corazon or custard-apple), while one from 

 several united flowers often partly from an en- 

 larged fleshy stalk is multiple (for example, higo 

 or fig) . 



Simple fruits are classed as dry or fleshy (juicy 

 or succulent) . Some dry fruits do not open to re- 

 lease the seeds (indehiscent), while others open 

 (dehiscent) . The akene is a dry fruit not openmg 

 and containing a single seed separate from the 

 fruit wall. The nut is also 1-seeded with a thick 

 hard shell. The pod or legume is a dry 1-celled 

 fruit which splits open usually along 2 lines (for 

 example, the legume family). The capsule is a 

 dry fruit of 2 or more cells which opens on as 

 many lines as cells. Fleshy fruits, which do not 

 open, include the herry. which usually has several 

 seeds, and the drupe, which has a central stone or 

 hard part containing 1 or more seeds. 



HOW TO USE THIS BOOK IN TREE 

 IDENTIFICATION 



Many trees can be identified by reference to the 

 drawings, descriptions, and distribution notes. 

 However, the illustrations alone may not empha- 

 size differences among closely related species not 

 figured. It is helpful to have for comparison the 

 flowers and fruits in addition to foliage because 

 many kinds of trees have leaves of similar shape. 

 Often one tree can be found in blossom out of sea- 

 son, perhaps at the edge of a fore.st, and old fruits 

 may be located on dead branches or on the ground. 

 A ruler and a hand lens are useful in examining 

 the specimen and comparing it with the descrip- 

 tion. 



If the local common name of a tree in Puerto 

 Rico or the Virgin Islands is obtained, such as by 

 asking residents, then the description, illustration, 

 and scientific name can be found by consulting the 

 page listed in the Index of Common and Scientific 

 Names. Since common names in other countries 

 and as many as five languages are included, the 

 Index will be helpful in determining the same spe- 

 cies elsewhere. 



To avoid errors, identification from a common 

 name should always be verified by inspecting the 



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