70 STRUCTURE AND PHYSIOLOGY OF SEED PLANTS 



most stringy portions are found, where the fibro-vascular 



bundles are most numerous. 

 D. Examine some ripe pods of the preceding year,* and notice 



where the dehiscence, or splitting open of the pods, occurs, 



whether down the placental edge, ventral suture, the other 



edge, dorsal suture, or both. 

 ■48. A schizocarp, the fnflt of caraway.'' Examine a complete fruit, 

 "caraway seed" (magnified). If it has not been roughly handled, 

 it should show the remains of the stigmas, surmounting the two 

 halves, mericarps, of the fruit. The mericarps are borne on a 

 forked stalk, from which they remain suspended until blown 

 away by the wind or otherwise detached. Make a cross section 

 of one mericarp (if dry, after soaking it for a minute or two in 

 hot water). Draw it magnified and label the pericarp, with its 

 oil tubes and the seed within. The tubes contain the volatile oil 

 which gives the fruit its characteristic smell and flavor. 



This fruit has no very effective means for securing dispersal. 

 Compare it in this respect with the fruits (commonly called 

 seeds) of parsnip and of carrot. 



49 . An akene, the fruit of dock. 



A. Hold in the forceps a ripe fruit of any of the common kinds of dock, 

 and examine with' the lens. Note the three dry, veiny, membranaceous 

 sepals by which the fruit is inclosed. 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. Cut off the tubercles from several of the 

 fruits ; put these, with some uninjured ones, to float in a pan of water, 

 and watch their behavior for several hours. What is apparently the 

 use of the tubercle ? 



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

 cling to the plant long after ripening ? 



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

 is its color, size, and shape ? 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 ? 



1 Preserved dry for the purpose. 



2 " Caraway seeds " can be bought from the druggists. 



