184 ELEMENTS OK BOTANY. 



natural position and the funiculus or stalk by which each is attached to 

 the placenta ; compare Fig. 176. 



Make a cross-section of another pod, through one of the beans, sketch 

 the section and label the placenta (formed by the united edges of the 

 pistil leaf), and the midrib of the pistil leaf. 



■Break off sections of the pod and determine, by observing where the 

 most stringy portions are found, where the fibro-vascular bundles are 

 most numerous. 



Examine some ripe pods of the preceding year,' and notice where the 

 dehiscence, or splitting open of the pods occurs, whether down the pla^ 

 cental edge, ventral suture, the other edge, dorsal suture, or both. 



217. An Akene, the Fruit of Dock. — Hold in the forceps a ripe fruit 

 of any of the common kinds of dock,^ and examine with the magnifying- 

 glass. Note the three dry, veiny, membranaceous sepals by which the 

 fruit is enclosed. On the outside of one or more of the sepals is found a 

 tubercle or thickened appendage which looks like a little seed or grain. 

 No use is known for this. 



Of what use are the sepals, after drying up ? Why do the fruits cling 

 to the plant long after ripening ? 



Carefully remove the sepals and examine the fruit within them. What 

 is its color, size, and shape ? Make a sketch of it as seen with the 

 magnifying glass. Note the three tufted stigmas, attached by slender 

 threads to the apex of the fruit. What does their tufted shape indicate ? 



What evidence is there that this seed-like fruit is not really a seed ? 



Make a cross-section of a fruit and notice whether the wall of the 

 ovary can be seen, distinct from the seed coats. Compare the dock-fruit 

 in this respect with the fruit of the anemone, shown in Fig. 169. Such 

 a fruit as either of these is called an akene. 



^ WMcli may be passed round for that purpose. They should have been saved and 

 dried the preceding autumn. 



" Rumex crlspus, li. obtusifolius, or li, verticillatus. This should have been 

 gathered and dried the preceding summer. 



