4 Fruits. [July, 



should be carefully removed, and on the other hand excessive 

 quantities should not be allowed to remain on to ripen. 



It is well known to all that the position of the seeds differs re- 

 markably in different species. In some they are arranged in regu- 

 lar order in a single cavity of the fruit; in others there are seve- 

 ral cavities. Sometimes they are attached to the centre of the 

 cavity, at others to the circumference, and again there seems to be 

 but little or no regularity in their arrangement. Sometimes they 

 are arranged on, apparently, a single line, and at others spread 

 over a large surface. Now, however various this arrangement 

 may be, the fact is universal, that they are always attached to the 

 edge of the leaf, or some development of it. The seed bearing 

 point, line or surface, as the case may be, is called the placenta, 

 and to trace its modifications, we trace the modifications in the 

 arrangement of the seeds. 



In the pea we see the fruit made up of a single leaf folded and 

 united by its edges, and bearing its seeds on two lines, at the line 

 of junction, that is, on the two edges of the leaf. Were it not 

 folded the seeds w^ould appear attached in a regular series along 

 the margin from the base on one side to the base on the other, 

 exactly as the miniature plants appear on the margin of the Bry- 

 ophyllum. There is a stage in the development of the fruit when 

 this is the case, in some plants at least, when the leaves that com- 

 pose the seed vessel are distinct and nearly flat, and the vesicles 

 that are to become the embryo, may be seen as small elevations 

 along their borders. As the parts increase, the leaves approach each 

 other, and become usually in some one of various ways soldered to- 

 gether, and variously folded. The soldering commences at the 

 base of the carpellary leaves and proceeds upwards, and in some 

 plants the soldering does not reach completely the apex, in which 

 case the seed vessel is lobed, as in the saxifragas and others. 



It is plain from the constitution of the seed vessel, that if it is 

 composed of but one carpel it can properly have but one cavity, 

 as the pea, bean, peach, cherry, &c., and that the number of cavi- 

 ties never can exceed normally the number of carpels, and if the 

 seeds are borne at the centre, there ought to be as many cells for 

 seeds as there are carpels, and if the seeds are attached to the 

 walls of the seed vessel, there ought to be no divisions into cells, 

 in other words, the fruit should be one-celled. These principles 

 are in conformity with facts, or if not, we can easily account for 

 the departure. We find in some cases seeds attached to a central 

 placenta, and the seed vessel one-celled. This has been produced 

 by the breaking up the dissepiment, or partitions, by the unequal 

 growth of the parts. In the early stage of the development, the 

 partitions were perfect, but subsequent expansion of the outer 

 walls ruptured the dividing membranes, and the vessel became 



