ADJUSTMENT TO TEMPERATURE 131 



means. Oftentimes hemeranthous flowers do not open at all 

 on unusually cool days, and nyctanthous ones fail to close. The 

 majority of nyctanthous species are ephemeral, while only about 

 one half of the day-bloomers are of this type. Flowers that open 

 and close daily may live for two days only, as in Erigeron and 

 Claytonia, or for two weeks, as in Crocus. Flowers that remain 

 open are long-lived as a rule. Many of them live for several 

 weeks, the maximum period being eighty days for Odontoglossum, 

 an orchid. The minimum period, three hours, is found in the 

 "flower-of-an-hour," Hibiscus trionum, which is the most ephem- 

 eral of all flowers. The study of the period of flowering and 

 of the time of opening and closing constitutes what is commonly 

 called phenology, i.e., a study of the phenomena of appearance. 

 While this is a fascinating field, its importance at present is 

 secondary. 



Experiment 42. Time of flowering. Select tea species which inchide 

 ever-blooming, day-blooming, night-blooming, and ephemeral plants, 

 and keep a tabular record during the spring of the time of day when 

 the flowers open and close, of the life period of a single flower, of the 

 time when the first flower appears, the maximum of the flowering 

 period, and its close. 



152. Fructification. The normal consequence of pollination 

 is the fertilization of the egg-cell of the ovule, and the development 

 of the latter into the seed. In the majority of flowering plants, 

 the ovary and its contents are alone concerned in the changes 

 of growth which follow fertilization. The ripening ovary of 

 this type becomes a simple fruit. In some cases, fertilization is 

 followed by a modification of the end of the flower-stalk, jiroducing; 

 a complex fruit, such as that of the apple, strawberry, blackberry,, 

 rose, pine, pineapple, Osage orange, etc. Fruits are usually classi- 

 fied with respect to their texture as (1) fleshy fiuits, including 

 stone fruits, and (2) dry fruits, and, with respect to their behavior 

 when ripe, as dehiscent or indehiscent. Fleshy and stone fruits 

 are indehiscent ; dry fruits may be dehiscent or indehiscent. 



153. Fleshy fruits are characterized by a thickening and 

 softening of the wall of the ovary, by which it becomes juicy or 

 fleshy. They comprise the berry, drupe, pepo, jjome. and such 

 multiple fruits as the fig and pineapple. In the Jjerry, e.g., the 

 currant, grape, gooseberry, tomato, etc., the whole tissue of the 



