2 THE AMERICAN BOTANIST 



Nearly all flowers open so gradually that the most careful 

 watcher cannot say positively that he has seen the petals move 

 but the evening primroses leave him in no such uncertainty. 

 He may indeed be 



"Startled by the leap 

 Of buds into ripe flowers" 

 as Keats expresses it. At the proper time the sepals, which 

 during the day have covered the bud, snap directly backward 

 in a business-like way and the sulphur-yellow petals, released 

 from their confinement, unfold at once and seem to settle into 

 their places with a sigh of satisfaction. The botanist, Lindley, 

 reported that at the instant of opening, a flash of phosphores- 

 cent light may be seen, but this statement seems to need con- 

 firmation. 



One of the most conspicuous examples of this rapid open- 

 ing, because of the size of the blossoms, is found in the Na- 

 vajo evening primrose, illustrated in our frontispiece. In 

 summer the first flowers begin to open about twenty minutes 

 of eight and the blooming proceeds so rapidly that one can 

 see. not a single blossom opening, but a whole bush bursting 

 into bloom. One is reminded of the way umbrellas begin to 

 appear in a crowd when a threatened shower begins to descend. 

 In ten minutes seventy-five flowers may open on a single plant. 

 The flowers in all the species are arranged in an indeterminate 

 inflorescence, two or three blossoms in the axil of each leaf 

 and though they open for only a single day— or night— there 

 are always one or two mature buds waiting to replace them at 

 the next dawn or dusk. 



The first flowers have scarcely spread before the hawk- 

 moths find it out. Attracted by the nectar they flock to the 

 flowers and for an hour or more are very busy; so busy, in 

 fact, that they pay no attention to human observers provided 



