APPENDIX 201 



16. The pistils are often united with each other. Here all stages 

 of union occur, from a slight union at the base to complete fusion 

 to the stigma. When the overies are united they form a compound 

 Gvary. This can be distinguished from a single simple ovary by 

 having several cavities or cells or by having several placentae. This 

 will be seen in a cross-section. Often they can be distinguished by 

 having several styles or stigmas. 



17. The floral structures of one series often unite with those of 

 adjacent series. Thus the stamens often unite with the corolla 

 especially in gamopetalous flowers as the morning glory or the 

 phlox. 



18. 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 structure is well shown in the straw- 

 berry blossom. This disc may grow upwards into a cup or tube as 

 in the plum or cherry. In these it disappears after the blossom 

 fades, but i nthe rose it is permanent and forms the flesh of the 

 hip and in the apple where it unites with the pistils and forms 

 the outer part of the flesh of the apple. In other plants, as in the 

 evening primrose, it 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 becomes inferior, and the flower epigynous. 



19. 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. 



20. The arrangement of the flowers i. e. the inflorescence is fre- 

 quently referred to in the keys. The names of the common flower 

 clusters will be given in the glossary-. 



21. After fertilization the ovary developes 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 formJng 

 the flesh of the fruit while the endocarp is horny and forms the shell 

 of the pit. 



22. Fruits which do not open are indehiscent, while those that 

 open at maturity to allow tht 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. 



23. 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 

 represented only by glands. The petiole may also be wanting, the 

 leaf is then sessile. 



24. In the grasses and sedges the lower part of the leaf sur- 

 rounds the stem and is called the sheath, the free part of the leaf 

 is the blade. In the grasses where the blade joins the sheath an 

 appendage called the ligule usually extends upwards around the 

 stem. 



