26 INTRODUCTION. 



water, the upper surface is provided with these stomata. The leaves of suc- 

 culent plants, as the Cactus, have but kw stomata, and hence have great 

 power in retaining the fluids absorbed by their roots. 



Stipules are small leafy appendages at the base of a petiole or sessile leaf, 

 of the same structure as the leaf. They do not occur in the larger propor- 

 tion of plants, and are always wanting in Exogens ; where their margins unite 

 so as to form a sheath round the stem, they are called ochrece. Leaves 

 having stipules are said to be stipulate, and when wanting these appendages 

 to be exstipulate. 



ORGANS OF REPRODUCTION. 



The organs of reproduction are those designed for the continuation of the 

 species. Every plant possesses some means of reproducing its kind, but these 

 differ exceedingly in the various tribes, from the simple evolution of new cells 

 in the lowest classes, to the complicated apparatus in the higher orders, of 

 which latter only, we shall speak at present. 



THE INFLORESCENCE. 



This term is used to express the manner in which flowers are arranged on 

 the plant. Flowers are called solitary when a terminal or axillary bud is 

 transformed directly into a flower. Opposite the leaves when the flower is at 

 the same height on the stem, and opposed to a leaf. Axillary when in the 

 axilla of a leaf. Extra-axillary when the flower grows from the side of the 

 origin of a leaf. Epiphyllous when arising from a leaf, and Terminal when 

 borne at the extremity of a stem or branch. 



When a flower is attached to a stem or branch by means of a stalk, this 

 organ is called a peduncle ; when there is no peduncle, the flower is sessile. 

 The peduncle is called a scape when it grows from the root. When it is 

 branched, each of the divisions is called a pedicel. 



Flowers are said to be in the form of a spike when they are sessile, and 

 placed simply along a common axis. A raceme is the same, except that the 

 flowers have pedicels. A spadix is a spike in which the flowers are close 

 set and enclosed in a spathe. A panicle is like a raceme, but the pedicels are 

 branched, long and distant. A corymb is the same as a raceme, with the 

 lower pedicels elongated so as to bring all the flowers on the same level. In 

 an umbel the pedicels arise from the same point, and diverge like rays'. In 

 a cyme the pedicels do not proceed from one central point. A thyrsus is a 

 panicle in which the pedicels are irregularly divided, the middle ones often 

 longer than the rest. A whorl is where the flowers are arranged in a ring 

 round the stem or branch. A catkin or ament is a spike with scaly bracts, 

 crowded together and usually falling off in a single piece. A head or capi- 

 tulum is formed of sessile or nearly sessile flowers, arranged in globular 

 form, its axis or rachis is called the receptacle. 



When the leaves which have flowers developed in their axils are smaller or 

 different from the common leaves of the plant, they are called bracts, those 

 of a very small size and near the calyx, are termed bracteoles. When they 

 arc set in a whorl at the base of the flower, it is called an involucre, and if 

 round a pedicel it is an involucel or partial involucre. A spathe is a large 

 bract or modified leaf enclosing flowers, before their expansion, and opening 

 longitudinally to make way for them. A glume or husk, peculiar to the 

 grasses, is something between a bract and a calyx ; within these are often 

 more delicate leaves or scales, which are called palece by some botanists ; this 



