80 APPLIED BIOLOGY 



structures containing seeds which develop from flowers. 

 Hence many things are known in biology as fruits which we 

 do not popularly call fruits; for instance, a tomato, a bean 

 pod, a squash, or a cucumber is in botany just as much a 

 fruit as an apple, a peach, or an orange. 



77. Study of a Bean Pod. (L) On a full-grown bean plant 

 about six weeks old one may usually find pods of various sizes, 

 ranging from one but slightly larger than the pistil of the flower up 

 to the size of the fully developed pod. The stalk of the pod is the 

 same as the flower- stalk or pedicel of the flower, and its expanded 

 end at the point where it is attached to the pod (fruit) is the recep- 

 tacle, which also may be seen beneath the flower. In the younger 

 pods, identify the calyx and the bracts of the flower, which can still 

 be seen at the stem end ; and at the other end find the style. 

 Between the calyx and the style is the ovary, which begins to 

 elongate shortly after pollination. If possible, examine the ovary in 

 a faded flower, just about the time that the corolla is ready to 

 fall off. Label sketches of young pods so as to show what parts 

 of the flower develop into the fruit. 



Study a full-grown bean pod (use green pods, known as "string- 

 beans"). Sketch and label, naming the parts by comparing with 

 younger pods. The pointed end is the base of the style, most of 

 which, with the stigma, was pulled off by the falling corolla. Note 

 that the pod is composed of two similar valves fastened together 

 along the edges, which are called sutures (meaning seams). The 

 bean pod is bilaterally symmetrical. The position of the style and the 

 concave curvature of the pod mark the edge or suture where the 

 seeds are attached. This is called a ventral suture, because it is down 

 or toward the ground in the natural position of the flower. The 

 opposite edge is dorsal. These terms are applied in the same way 

 to animals, the upper side or back always being the dorsal, and the 

 ventral the opposite side toward the earth. 



Carefully split open a green pod along the dorsal suture and note 

 that some beans (or seeds) are attached to each half of the pod. 

 Is there any regularity as to the number attached to either half ? 

 Note that each bean is held in place by a short seed-stalk (funiculus). 

 Undeveloped ovules may be seen near the ends of the pod. The part 

 of the inner lining of the pod to which the seeds are attached is 

 known as the placenta. Make a labeled sketch of the opened pod, 

 showing the seeds in position. 



