STUDIES OF FEUITS 73 



Note the toughness and thickness of the seed coats. Taste 

 the kernel of the seed. 

 G. Cut a very thin slice from the surface of the skin, mount 

 in water, and examine with a medium power of the micro- 

 scope. Sketch the cellular structure shown, and compare it 

 with the sketch of the cork of the potato tuber. 



Of what use to the fruit is a corky layer in the skin ? 



Reference. Strasburger-Hillhouse, 6. 



53. A drupe, the cherry. Make a cross section of a partly grown cherry, in 

 which the stone has not become too hard to cut. Make a magnified sketch 

 of it, showing the double pericarp, consisting of the exocarp, or fleshy part, 

 covered with a thin, tough epidermis, and the endocarp, or stone, containing 

 the seed. Crack some ripe cherry stones and study the seeds. 



If possible, compare with the structure of the cherry that of other drupes, 

 such as the peach, the fruit of the cocoanut (with the husk), the entire 

 fruit (with husk) of walnut, butternut, or hickory nut, and the fruit of the 

 Cornus, or dogwood. 



54. An accessory fruit, the strawberry. 



A. Study the flower of a strawberry, noting particularly the number, 

 shape, and position of the pistils. 



B. Examine a series of strawberry fruits,^ beginning at the time when 

 the cluster of pistils shows signs of enlarging. How much does each 

 pistil enlarge ? What causes the increased size of the fruit ? 



C. Study a firm, ripe strawberry with the lens, and draw the ripened 



pistils, called akenes. 

 T). Cut a lengthwise section of the fruit and sketch it. 

 What is the main difference in proportions between a head of akenes, like 



that in Principles, Fig. 161, and a strawberry ? What is the use of the 



pulpiness of the ripened receptacle ? 



55. Development of » fruit. Secure a series of as many stages as possible 

 in the development of some convenient fruit, as the common bean, from the 

 newly fertilized pistil to the full-grown pod.^ 



A. Make drawings of the entire fruit, the earlier stages x 4 or x 5, but 

 all the later ones natural size. 



B. Cut thin cross sections and lengthwise sections (through the seed) of 

 a series of fruits and sketch them, using a magnification of about 20 



1 Material preserved in alcohol will answer. 



2 Other leguminous fruits, or any moderately large capsules or berries, will an- 

 swer. Material in preservative fluid suffices for all but the study of the course of 

 absorbed liquids. 



