SUGGESTIONS 205 
fusion to the stigmas. A pistil formed by the fusion of two or more 
carpels is called compound and can usually be distinguished from a 
single simple pistil by the ovary having several cells or several 
placentas as shown in cross-section. They often have several styles 
or stigmas. 
15. Floral organs of one series are often united to those of an 
adjacent series, the stamen filaments for instance are often united 
to the corolla in gamopetalous flowers. 
16. In many flowers the lower part of the receptacle is ex- 
panded into a disc or hypanthium on the edge of which the perianth 
and stamens are borne. This disc is present in the strawberry blos- 
som, and persists at the base of the fruit. In plums and cherries 
the hypanthium is cup shaped and surrounds the pistil, but disap- 
pears when the blossom fades. In the rose it persists and forms the 
fleshy part of the hip and in the apple it is united to the carpels 
and forms the outer part of the fruit. In some of the evening prim- 
roses the hypanthium forms a tube extending beyond the ovary. 
When the hypanthium reaches to the top of the ovary or beyond 
and is adnate to it, the ovary is inferior and the flower is epigynous. 
17. When all the members of each whorl of floral organs are 
alike or nearly so the flower is regular; if they differ from each 
other, one side of the flower being markedly different from the 
other, it is irregular. 
18. The arrangement of the flowers, i. e., the inflorescence, is 
frequently referred to in the keys. The names of the common flower 
clusters will be given in the glossary. 
19. After fertilization the ovary develops into the fruit. The 
walls of the ovary form the pericarp, which consists of two layers, 
the inner is the endocarp, the outer the exocarp. These are often 
quite different, for instance in the plum the exocarp is juicy, form- 
ing the flesh of the fruit, while the endocarp is horny and forms the 
shell of the pit. 
20. Fruits which do not open are indehiscent, while those that 
open at maturity to allow the seeds to escape are dehiscent. Most 
dehiscent fruits split lengthwise into valves or teeth. If they have 
several cavities they may open at the middle of the cavities or at 
the dividing walls between them. The former is called loculicidal 
and the latter septicidal dehiscence. If the fruit breaks regularly 
crosswise, the top coming off like a lid, it is circumscissile. 
21. A leaf may have three distinct parts, the blade, the stalk, 
or petiole and the stipules. The blade is the expanded green part 
forming the main portion of the leaf. Leaves with more than one 
blade are compound. The stipules are small appendages on the sides 
of the petiole at its base. They are frequently wanting, or repre- 
sented only by glands. The petiole may also be wanting, the leaf is 
then sessile. 
22. In many monocotyledons such as the grasses and sedges 
the leaf consists of a sheath surrounding the stem and a free part 
or blade. Where the blade and sheath join a collar-like appendage 
called the ligule often surrounds the stem. 
_ 23. The leaves accompanying the inflorescence are often quite 
different in forms, size, and sometimes in color from the ordinary 
foliage leaves. Such modified leaves are called bracts. A whorl of 
