228 Introduction to Botany. 



waste ? Has the flower an odor that we can perceive ? (See 

 page 182 about the sense of smell in insects.) Describe 

 the color plan in this flower. 



Study Cypripedium in its native habitat. Is it common 

 or of infrequent occurrence ? Can you see reasons for 

 what you find in this regard ? Tie a string about the base 

 of a newly opened flower to mark it, and note how many 

 days the flower lasts. Note what insects visit the flower 

 and whether their visits are frequent, and watch them 

 enter and leave the flower. Note what per cent of the 

 flowers become fertilized and produce seeds. 



The Orchidacese, to which family Cypripedium belongs, 

 show marked affinities to the Liliacese, Amaryllidaceae, 

 and Iridaceae (see studies of Erythronium, Hypoxis, 

 Sisyrinchium, and Iris). Comparing the flower of Cypri- 

 pedium with that of a lily, we find that they are similar in 

 having three outer and three inner perianth parts, and 

 three carpels composing the pistil ; but we find that the 

 ovary of the Orchidaceas is inferior, the upper half of the 

 flower is unlike the lower half, the sepals and petals are 

 irregular, and the stamens are reduced in number and 

 apparently joined to the style. The different genera of 

 the family show marked specialization of the flower to 

 secure cross pollination by insects (see description of 

 Catasetum on page 190). In Cypripedium the lower petal 

 or lip (morphologically the upper petal but turned down- 

 ward by a twist in the ovary) forms an overarched cavity 

 into which the insect must go to secure the nectar. While 

 the insect very naturally enters the cavity through the large 

 opening on top, it finds itself prevented from going out that 

 way by the dome-like form of the upper part. Two rela- 

 tively small openings on either side of the united style 

 and stamens do not present this difficulty, and the anthers 



