20 A FLORA OF MANILA 



largest group of flowering plants is subdivided into two great divisions, 

 the monocotyledons, if one cotyledon be present, and the dicotyledons, if 

 two be present. When the embryo proper contains its own store of plant 

 food, the seed is called exalbuminous, but when the plant food is stored 

 outside of the embryo the seed is called albiiminotis, and the food-deposit 

 is called the endosperm. In descriptive botany the endosperm is described 

 as mealy when granular like meal, horny when hard and bone-like, con- 

 tinuous when smooth and uninterrupted, and ruminated when penetrated 

 with irregular depressions, as if chewed, as in the betel nut (bunga). 



CLASSIFICATION 



Recent estimates show that there are at present known in all groups 

 of plants about 235,000 different kinds or species, hence it is evident that 

 some kind of systematic classification is necessary to indicate the relation- 

 ships of this enormous number of forms. For convenience botanists have 

 classified plants according to their relationships or assumed relationships 

 into species, genera, families, orders, etc., all finally being included under the 

 comprehensive term Vegetable Kingdom. 



■ A species comprises all the individuals that so closely resemble each 

 other that we may, conclude that they hdve all been descended from a 

 common parent, from few to many generations back. Specific identity is 

 inferred when different specimens closely resemble each other in all essential 

 characters, for no two individuals are exactly alike, there always being a . 

 tendency to variation; under species some botanists recognize subspecies, 

 varieties, and forms, but it is frequently if not always a matter of personal 

 opinion whether any constant character or set of characters by which one 

 plant differs from other allied ones, constitutes a specific difference, or 

 whether the differences should be considered only as the basis of a sub- 

 species, a variety, or a form. 



To facilitate classification a number of species having certain characters 

 in common, are grouped in a genus; the generic name corresponding to 

 a person's family name, and the specific name to his given one; a genus 

 may consist of a single species, or of any number up to several hundred. 

 Genera are frequently subdivided into subgenera or sections, or both. 



Genera still being far too numerous properly to study without other 

 arrangement, have been grouped into families, each family . having its 

 distinctive name; for instance, the Palmae or palm family form a very 

 natural group, the limits of which are evident even to non-botanical ob- 

 servers; the grasses form another equally well-marked family, the sedges 

 another, etc. Families may contain few to many genera, and are fre- 

 quently divided into subfamilies and tribes, or they may consist of a 

 single genus with but few, or sometimes only a single species. 



Families themselves, of which about 285 are now generally recognized 

 in the flowering plants, are again arranged in orders; the grasses and 

 sedges, for example, being two distinct families but with cei-tain characters 

 in common that are not found in other groups, are hence classified in the 

 natural order Glumales or Glumiflorae. Orders are arranged in Classes, 

 the Order Glumales falling in the Class Monocotyledoneae with many 

 others, that is, plants which produce seeds with but a single cotyledon. 

 Again Classes are grouped in Divisions, the Class Monocotyledoneae forming 

 a Subdivision of the Anpiospcrmae, that is, plants with ovules borne in 

 closed ovaries, of the Division Spcrmatophyta, that is, all plants that 

 produce seeds. The Vegetable Kingdom is made up of four Divisions. 



