4o6 



THE SCITAMINALES 



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. 



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, 

 5, the other organs being removed. 



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

 highest group of the monocotyledons and their flowers are a 

 source of wonder and admiration, owing to the singular beauty 

 and delicacy of their mechanical construction. Variation in this 

 order has occurred on a gigantic scale, resulting in a larger num- 

 ber of species (over 7,000) than is found in any of the preceding 

 orders. Nevertheless these elaborate variations have not been 

 very successful in enabling them to compete with other plants, 

 and as a result the orchids are rather rare and not at all com- 

 parable in number of individuals with the lilies and grasses. 

 Though more widely distributed than any of the other monocoty- 

 ledons, their variations have adapted them as a rule to peculiar 

 conditions. They are especially abundant in the mountainous 



