SUPPRESSIONS, ALTKRATIONS, APPENDAGES 219 



are very common and are a frequent cause of irregularity 

 and want of symmetry, as was seen in the stamens of the 

 cress family (Sec. 295). Suppressed stamens are a com- 

 mon characteristic of the great bilabiate group (Sec. 308), 

 large numbers of species having only two or four, but 

 these are often accompanied^ as in the pentstemon, che- 

 lone, and figwort, by sterile filaments in a more or less 

 aborted condition that carry out the ^j, 



law of symmetry indicated in the five- 

 lobed corolla (Sec. 308). The fila- 

 ment and style are often wanting, so 

 that the anther or the stigma becomes 

 sessile. While it is usual to speak of 

 the stamens and pistil as essential 

 organs, it is really only the ovary and 

 the anther, or more strictly speaking, 

 the ovules and pollen that are absolutely 

 essential. The style is merely an ap- 

 pendage for placing the stigma where 

 it will be brought more easily into con- 

 tact with the pollen, and may be of any 

 length, from a foot or more, as in the 

 "silk" of the Indian corn, to a mere 

 line, or entirely absent, as in the poppy 

 and some of the yuccas. 



The study of these rudimentary or 

 discarded organs helps to explain many 

 deviations in the structure of flowers 

 that would otherwise be very puzzling, and by their aid 

 we can often reconstruct the plan of a flower that seems 

 to have lost all conformity to the type. 



440 



439, 440. — Abortive 

 stamens {after GRAY) : 



439, CQXoWaLQi Pentstemon 

 grandiflorus laid open, 

 with its four stamens, and 

 a sterile filament in the 

 place of the fifth stamen ; 



440, corolla of catalpa 

 laid open, with two per- 

 fect stamens and the 

 vestiges of three abortive 

 ones. 



314. Cleistogamic {closed ) Flowers are so called because 

 they never unfold, but are pollinated in the bud. Common 

 examples are the inconspicuous closed flowers, on very 

 short peduncles, concealed under the leaves of most 

 violets. Sometimes, as in the fringed polygala, they are 

 borne on underground stems and never rise above ground at 



