212 PRACTICAL LESSONS IN SCIENCE. 



When there are six, four long and two short, they are tetradyna- 

 movs. The variety of positions in which stamens are found has 

 led some authors to doubt whether they are changed leaves, 

 considering them as possibly outgrowths from the epidermal 

 system of the plant. 



The anther consists of two lobes or cells in which pollen grains 

 are formed, that contain the fertilizing element of the plant. 

 When the anther is attached by its base to the apex of the fila- 

 ment, it is innate; when attached for its whole length to the side 

 of the filament, it is adnate, and when fixed near the middle to 

 the apex of the filament, it is versatile. When it faces inward, it 

 is introi'se; when outward, it is extrorse. 



The upper or innermost whorl of the floral leaves form the 

 pistil or pistils. A pistil consists of a stigma, style and ovary. 

 The ovary is the enlarged hollow part of the pistil in which the 

 ovules are formed, the part from which the ovules arise being 

 called the placenta. Above the ovary the pistil narrows into the 

 style which bears the stigma, which is a moist, glandular body of 

 varying shape. There may be several pistils in one flower; or two 

 or more may unite, forming a compound pistil. If we think 

 of the ovary as formed from a leaf by bringing its edges to- 

 gether, the line of union is called the inner suture, and a line cor- 

 responding to the midrib of the leaf is called the outer suture. 

 The inner or ventral suture is the placenta. When two or more 

 ovaries unite to form a compound ovary, the union is usually 

 along their ventral sutures so that the ovules are attached to a 

 column in the center of the ovary; and sometimes the partitions 

 dissolve away and a one-celled compound ovary results with the 

 ovules on a stalk in the center. 



In some compound ovaries the ovules are on the walls and not 

 in the center. We may imagine in such cases that the three 

 or four or more leaves forming the ovary united with each 

 other by their edges, thus forming ventral sutures at the junc- 

 tion of two leaves instead of at the junction of the edges of the 

 same leaf. In one case the placenta is central, in the other it is 

 said to be pariet&l. 



