4 EXPLANATION OF THE TERMS USED 



applied generally in this book to any group of flowers having a common stalk, 

 but not coming under the definition of a raceme or panicle. ^ 



Compound Leaf. When the blade of a leaf is divided into two or more separate 

 leaflets, each with its own stalk or independent base, the leaf is said to be com- 

 pound. That the leaflets themselves are not leaves is shown by the absence of 

 buds in their axils; also the whole leaf can be pulled off as one, leaving a well- 

 defined scar on the stem. (Figs. 1-23.) 



Corolla (C). The petals taken together. Denoted in the floral formulae by the 

 letter C. 



Deciduous (D). Falling oflF, not persistent. A deciduous tree or shrub is one 

 which normally loses all or most of its leaves, i.e. becomes bare, during a definite 

 season of the year, usually the winter. 



Dicotyledon. See page 143. 



Digitate. Used in this book of a compound leaf of 2, 4, or more leaflets, which all 

 arise from approximately the same point at the end of the common stalk. (A 

 leaf of 3 leaflets can also be digitate, but the distinct term T^-foliolate has been 

 used here for such leaves owing to their large number.) (Figs. 4-6.) 



Embryo. The rudimentary or 'unborn' plant tucked away inside the seed before 



germination. 

 Entire. Without teeth or lobes. 

 Evergreen (E). Clothed with leaves throughout the year, not deciduous. Plants 



that are normally leafless are also described as evergreen when the branches or 



any other parts assuming the functions of leaves remain green throughout the 



year, e.g. gorse and broom. 



Flaccid. Not stiff or rigid. 



Floral Formula. A method of compressing information, used by botanists for 

 many years. K stands for the calyx, C for the corolla, A for the stamens, and 

 G for the pistil. G means that the pistil has a superior ovary (see Ovary), 

 G an inferior ovary, G that both superior and inferior ovaries may be present. 

 The figure after each indicates the number of parts of which it is composed ; if 

 the figure is enclosed in brackets the parts are all joined together, i.e. they 

 cannot be pulled off separately without tearing. For instance, the floral formula 

 of the family Diapensiaceae is K (5), C (5), A5, G (3), which means that the 

 flowers of this family have 5 united sepals, 5 united petals, 5 separate stamens, 

 and a superior pistil formed by the union of three originally separate parts 

 (carpels). Other symbols used are : P (perianth), 00 for numerous or an indefinite 

 number, and + inserted between figures to show the separation of the parts 

 into two or more layers or whorls. 



G. See Floral Formula and Pistil. 



Genus. Plural genera, adjective generic. The genus of a plant is indicated by the 

 first of its two Latin names, e.g. in Qiiercus coccinea the tree belongs to the genus 

 Quercus. Oiiercus is the generic name, coccinea the specific name (see Species). 

 There is no absolute rule as to what constitutes a genus. All that can be said is 

 that species which show several distinct characters in common are usually 

 grouped together in one genus. In Quercus (Oak) the most easily recognizable 

 common character is the acorn. Allied genera are grouped into Families, 



^ A branched cluster, in which the central flowers open first, is known as a cyme. (Fig. 

 65 H.) When the outer flowers open first it is a corymb. (Fig. 93 H.) These terms have 

 not been used in this book, for they are often difficult to determine. 



