110 



PRACTICAL BOTANY 



The flowers of monocotyledons and of dicotyledons very 

 commonly have separate sepals and separate petals (Fig. 92). 



The sepals and petals are then 

 said to be distinct. In the more 

 specialized and higher families, 

 both of monocotyledons and 

 of dicotyledons, the receptacle 

 often bears a tubular or cup- 

 like outgrowth, and the peri- 

 anth is borne upon this. In 

 such cases the sepals, the pet- 

 als, or both, appear as if grown 

 together into a tube, upon the 

 free border of which are seen 

 teeth, or lobes, which indi- 

 cate the number of divisions 

 of which the perianth is com- 

 posed (Fig. 97). 1 



Sympetalous corollas occur 

 of many extraordinary forms, 

 enabling them to aid in seed 

 production. The only such co- 

 rolla shown in this book is 



Baillon and Luerssen the fypripedmm of the Orchis 



family (Figs. 281 and 282). 



100. Forms of the stamen; union of stamens. A common 

 form of stamen is that shown in Fig. 100, A, consisting of an 

 enlarged portion called the anther, borne by a slender stalk 

 called the filament. When the filament is lacking, the sta- 

 men is said to be sessile. Sometimes the filaments appear to 

 be united, thus joining the stamens into one, two, or more 



1 When the sepals are distinct the flower is said to be chorisepalous (sepa- 

 rate sepals) ; when the petals are distinct, choripetalous. When the sepals 

 or petals appear only as teeth or lobes on the margin of a tubular or cup-like 

 outgrowth of the receptacle, the calyx is said to be synsepalous and the. corolla 

 sympetalous (syn signifies " together "). The terms gamosepalous and gamo* 

 petalous are also used (gamos signifies ''marriage" or "union"). 



FIG. 99. Diagrams to show struc- 

 ture of an anther 



A, younger stage, with four chambers 

 or locules(loc) containing pollen mother 

 cells dividing to form pollen grains; 



B, an older stage in which the pollen 

 grains (p) are fully formed and each pair 

 of locules is uniting to form a pollen sac, 

 which will split open and discharge 

 along the line of dehiscence (d) . After 



