THEORETICAL STRUCTURE. 41 



81. The OVULES are certain little globular bodies, produced in 

 the cells of the ovary, destined to become the seeds in the 

 matured fruit (Fig. 10; 1.) 



82. The PLACENTA is that part of the ovary from which the 

 ovules arise, and to which they are attached. It consists of a 

 line, or fleshy ridge, placed in some angle of the cell. Its direc- 

 tion is always vertical, that is, parallel with the axis of growth. 

 (Fig. 10; l,d.) 



83. Physiological structure. The ovary and style are com- 

 posed chiefly of one or more bundles of vascular tissue, imbed- 

 ded in cellular tissue. The stigma consists of a loose cellular 

 substance, called the conducting tissue, communicating with the 

 placenta through the centre of the style. It is the only part of 

 the ascending axis which is destitute of the epidermis (35). 



84. Theoretical structure. The pistil, as before stated (25, a), is the modifica- 

 tion of a leaf, or of a whorl of leaves, each leaf constituting a carpel. Each 

 carpel has its own style and stigma, and is formed of a leaf folded together in 

 such a way that the upper surface becomes the inner, and is turned towards the 



The 15th class, Tetradynamia, is divided into two orders, which are distinguished 

 by the form of the pod : 



1. Siliculosa, the fruit a silicic, or short pod. 



2. Siliquosa, fruit a silique, or more or less elongated pod. 



The orders of the 15th, 17th, 18th, 20th, 2lst, and 22d classes are of. the same 

 name and character as the first 13 classes themselves, that is, they are founded 

 upon the number of the stamens to the flower, thus : 

 Order 1, Monandria, includes all Monadelphous plants, Diadelphous plants, &c. 



with one stamen to each flower. 



2, Diandria, with two stamens to each flower, and so on. 

 The orders of the 19th class, Syngenesia, are five : 

 Order 1. Equalis (equal), with the florets (flowers) of the head all perfect. 



2. Superflua (superfluous), florets of the rays, or margin of the head pistil- 



late r the rest perfect. 



3. Frustranea (frustrated), florets of the margin neutral, the rest perfect. 



4. Necessaria (necessary), florets of the margin pistillate and fertile, the rest 



staminate and sterile. 



5. Segregata (separated), each floret having its own proper calyx. 



The orders of class 23d, Polygamia, are two, founded upon the same characters 

 as the two preceding classes : 



1. Moncecia, where both separated and perfect flowers are found in the same 



individual. 



2. Dioecia, where the different flowers occupy different individuals. 



The orders of class 24th, Cryptogamia, are nine, the same as the natural orderi 

 of this grand division, as Filices, the ferns, Musci, the mosses, &c 



