DEVELOPMENT OF PLANTS 



421 



fruit. The ability of these plants to propagate themselves by 

 means of buds developed on the underground rhizomes may have 

 resulted in the loss of the seed habit. A great many plants are 

 so successful in propagating themselves by buds, bulbs, runners, 

 etc., that they have ceased to produce seed. In the higher mem- 

 bers of the order, as in the ginger and canna families, the flowers 

 become very irregular through the unequal development of the 

 leaves of the perianth or in some forms on account of the abor- 



FiG. 290. Flower of Canna, the showy petal-like organs being modified 

 stamens (staminodia) while the perianth proper, p, is reduced to green bract- 

 like organs: /, labellum; an, anther on petal-like organ; s, stigma; 0, ovary. 

 B, section of flower, showing ovary, 0, the modified stamen, an, and stigma, 

 s, the other organs being removed, 



tion or transformation of all the stamens save one into petal-like'^- — 

 organs termed staminodia. Usually one of the leaves of the 

 perianth, or one or more of the staminodia, are highly modified 

 and known as the labellum. This organ is so placed as to afford 

 a natural landing place for the insects visiting the flower and also 

 to necessitate crossing (Fig. 290). Observe a bee visiting the 

 flowers of the canna and determine the significance of the position 

 and movement of the labellum and its relation to the stamen and 

 stigma. 



135. Orchidales, the Orchid Order. — The orchids are the 



