10^4 



A TEXTBOOK OF THEORETICAL BOTANY 



The reproductive parts come next; firstly the stamens, making up the 

 androecium, and lastly the carpels, forming the gynoecium. The in- 

 sertion of the parts on the receptacle may be wholly spiral, or wholly in 

 whorls, that is, cyclic, or partly one and partly the other, spirocyclic. 

 In most cyclic flowers there is a strict alternation in the position of parts in 

 successive sets, but this is not true of spiral flowers. 



Organs of one set may be coherent or united together, or they may be 

 free (Fig. 1054). Organs of dift'erent sets may also sometimes be adherent 

 together. 



Fig. 1054. — Passiflora coenilea. Transverse section of 

 a flower bud. All the parts are free except the three 

 carpels in the centre, which are coherent. (After 

 Van Tieghem.) 



Cohesion afi^ects chiefly the petals, which are either apopetalous (free) 

 or sympetalous (joined), and the carpels which are either apocarpous or 

 syncarpous. Cohesion of the stamens is less commonly found, but they 

 are frequently adherent to the petals, when they are said to be epipetalous. 



The stamen consists of a stalk or filament, on which is borne a head or 

 anther. The anther is a four-lobed structure, each lobe containing a 

 pollen -sac, and the four lobes are united round the upper prolongation of 

 the filament, called the connective. Each pollen-sac or loculus contains 

 pollen grains, the microspores of the Angiosperms, which are exposed 

 when the anther splits open (dehiscence) at maturity. The carpel generally 

 consists of three parts: the ovary, a hollow structure enclosing one or more 

 ovules; the style, which is a columnar prolongation of the ovary wall, 

 terminating in the stigma, an adhesive surface on which the pollen is 

 received. 



In addition to the above parts, there are also, in many flowers, nectaries 

 or honey glands, which may be either outgrowths of the receptacle, or may 



