MORPHOLOGY OF AXGIOSPERMS. 129 



When a flower has but one stamen it is termed monandrous; 

 and when there are two. ihree or many stamens, it is said to be 

 diandrous, triandrous or polyandrous [Vig. 84). TIk' aggreg-atc 

 of stamens in the flower is eafled the andrgcii;.m. In tlie Labi- 

 atse there are four stamens arranged in a longer and sh(n-ter pair 

 and the stamens are said to be didv.xamgus ; in tht- CrueifercC 

 the flowers possess six stamens, four of which are longer than th.e 

 other two, and the stamens are described as Ti-rrRADYNAMOUs ; 

 in some plants, as in the Lobeliacese, PapilionatcC, etc., the fila- 

 ments cohere, forming groups f Fig. S2) which are termed mona- 

 delphous, diadelphous. etc. : in the flowers of the potato the 

 anthers lie close together Init are not united, forming apparently 

 a continuous ring or band around the pistil, when they are said 

 to be connivent ; in the tubular flowers of the Compositae the 

 anthers are united, forming a closed ring, and the stamens are 

 spoken of as syngenesious (Fig. 82. A) ; in many of the Ciiciir- 

 bifacccc the filaments and anthers both are confluent : in the flowers 

 of the Orchidacese the stamens are borne upon the pistil and arc 

 said to be gvxandrous (Fig. 133). 



Floral Envelopes. As their name indicates the floral 

 envelopes occupy the outermost or lowest position in the arrange- 

 ment of the parts of the flower. In the bud condition they protect 

 the essential elements, and in the exixmded flower are considered 

 to play an important role in securing pollination through the 

 visitation of insects. The floral envelopes -^re made up generally 

 of two kinds of leaves, petals and sepals (Fio;. 83). 



The PETALS form a spiral which surrounds the adrcecium. 

 They are as a rule quite bright and attractive, being frequently 

 highly colored, as in the rose, Fuchsia, violet, etc., and are known 

 collectively as the corolla. 



The SEPALS form the next and lowermost spiral. They are 

 usually green and leaf-like, as in the rose and carnation, and 

 together constitute the calyx. Sometimes the corolla and calyx- 

 are spoken of together as the i-eriaxtii. although strictly speak- 

 ing the term has a more special api)lieation. and is used mostly m 

 speaking of the sepals and petals of monocotyledonous flower.s, 

 these parts being much alike and not distinguishable, save in posi- 

 tion, as in certain lilies. 



