40 ELEMENTARY BOTANY. 



parts are exactly alike, that is, all the sepals alike in shape 

 and size, all the petals alike in shape and size, and all the 

 stamens alike in shape and length, the flower is said to be 

 regular. If this likeness in shape, size, etc. does not obtain 

 in any one or more of the organs, the flower is said to be 

 irregular. If the petals, sepals and stamens are of the same 

 number, or the latter may be twice or thrice as many, the 

 flower is said to be symmetrical ; but if the number is differ- 

 ent in different whorls, the flower is said to be unsymmetrical. 



6. When the relative insertion of the floral parts is exam- 

 ined, two types are found to prevail. In one case each petal is 

 inserted direcfly in front of, or within, a sepal, and each stamen 

 directly in front of, or within, a petal ; the parts are then said 

 to be opposite. But in the other case the petals are in front of, 

 or directly within, the spaces between, that is, alternate with the 

 sepals, and the stamens alternate with the petals ; then the parts 

 of the flower are said to be alternate. When the parts of the 

 flower, especially of the calyx and corolla, are each three in num- 

 ber, the flower is said to be three-parted. Monocotyls generally 

 have three-parted flowers. If the parts are each four or five in 

 number, the flowers are respectively four- or five-parted ; the 

 five-parted flowers are generally characteristic of Dicotyls. 



7. When the sepals are free or distinct from one another, 

 the calyx is said to be chorisepalous (Gr. choris, asunder), and 

 when the petals are free, the corolla is choripetalous. The 

 terms polysepalous and polypetalous, instead of the preceding, 

 have generally, though incorrectly, been used in descriptive 

 botany. The sepals may be united edge to edge, so that only 

 their upper ends are free, by which the number forming the 

 cup or calyx may be determined. The calyx in such case is 

 said to be gamosepalous (erroneously called monosepalous). 

 When the petals are united the corolla is gamopetalous (Fig. 

 58). The term monopetalous is erroneously used with the 

 same signification. This union of similar parts, or cohesion, 

 gives rise to a variety of forms of the calyx and corolla, 

 prominent among which are : — rotate, salverform, campanu- 

 late, funnelform, tubular, labiate and ligulate. 



