INTRODUCTION xv 



subtending- the flower, as well as bracteoles, and also the axis upon which the 

 flower is borne. 



A vertical section of the flower may also be drawn, in which the floral organs 

 are sketched more or less naturally. 



Classification of a plant may follow the description. Such work is preliminary 

 to a knowledge of the unit of classification, the species. Flowering- plants, accord- 

 ing to the Natural System, are called Phanerogams. 



This major division includes: 



Angiosperms Ovules enclosed in an ovary. 

 Gymnosperms Ovules not enclosed in an ovary. 



The only native British Gymnosperms are Pine, Yew, Juniper. 

 The Angiosperms include: 



Dicotyledons 2 cotyledons, leaves net-veined, vascular bundles open. 



Floral organs in fives, fours, or twos. 

 Monocotyledons i cotyledon, parallel -veined leaves, vascular bundles 



closed, scattered. Floral organs in threes or multiples thereof. 



Dicotyledons and Monocotyledons are subdivided into several sub-classes, and 

 the latter into about ninety natural orders or families (described in Vol. V). 

 It is more difficult to acquire at once a knowledge of these on account of their 

 number, but it should not be difficult even for the tyro to master empirically the 

 characters of many of them without any actual acquaintance with the essential 

 scientific characters of the order. Thus the order Ranunculaceae is not easily con- 

 fused with many others (save perhaps Cistaceae or Rosaceae) owing to its distinct 

 petals (and sepals) and hypogynous stamens. In Rosaceae the calyx is gamo- 

 sepalous, and the stamens perigynous or epigynous. The order Cruciferae, with 

 4 petals arranged in cruciform order, is fairly well marked, and has uniformly 

 4 long and 2 short stamens. The Umbelliferae have a characteristic umbellate 

 inflorescence, 5 sepals, petals, and stamens, and an unmistakable fruit, a schizo- 

 carp, of 2 mericarps. 



It is a good plan to master a few orders at a time, and then by a process of 

 elimination the reference of a plant to its natural order becomes less difficult. 



More troublesome is the knowledge of genera, the next stage in the classifica- 

 tion of plants. Of these the British Flora contains over 500, hence a proper 

 knowledge of these must take time. For a description of these see the summary 

 following that of the natural orders (Vol. V). The relationship of the various 

 divisions and lower grades of classification of plants has already been defined in 

 Vol. I, in the preliminary remarks prefacing the analytical summary. 



In studying these different groups one must again emphasize the need for 

 learning their meaning with specimens always, where possible, beside them. 



When the species is being studied, in a genus consisting of more than one 

 species (as is usually the case), this becomes most difficult. One must then make 

 use of a good flora (as to which see advice given below). 



In studying plants it is almost essential to dissect the specimens to be examined. 

 This at once gives an insight into the structure and the composition of a flower, 

 the part especially important in classification. For this purpose should be procured 

 a knife for cutting sections through a structure. For laying out or separating 

 the parts of a flower, one or two teazers or needles mounted in a match or similar 

 handle are required. A pair of fine-pointed scissors may be used for cutting out 

 fine structures where a knife would be too clumsy. In order, when the various 



