DEGENERACY OF FLOWERS. 



2G1 



Cleistogamoua 

 flower-bud of Impatiens 

 ftUva ; b, stamens (after 

 Bennett). 



the permanent forms of the flowers of 0. cornicidata, which I 

 at first inferred, from the wide distribution of this species, 

 must be habitually self-fertilising. From Fig. 57, a, it will be 

 seen that the corolla just protrudes from the closed sepals, 

 and always remains as a " cap," b. Of the ten anthers, five 

 are often abortive or wanting, d ; the fertile anthers are 

 placed over the very short stigmas, and are bound together 

 by fine threads. These appear to play some part, bat the 

 nature of their function is obscure, c. 



Impatiens fulva and I. Noli-me-tangere have also cleisto- 

 gamous flowers. Fig. 58, a, represents 

 a bud, and h two metamorphosed sta- 

 mens. 



Lamiuin amplexicaide will furnish, 

 another example of cleistogamy. This Fig. 58 

 genus has usually flowers highly differen- 

 tiated, and adapted to insect fertilisation. 

 That the cleistogamous flowers of this, as of all other species, 

 are detrraded forms of the normal kind is obvious fi'om the 

 presence of the "lip," as well as by there being four and 

 didynamous stamens. The style elongates very much, and 

 under the pressure of the closed 

 summit of the corolla becomes bent, 

 so that the stigmas lie between the 

 anther-cells, and thus readily become 

 fertilised. Fig. 59, a, represents a 

 flower-bud ; b, the corolla in section ; 

 and c, the pistil removed. This Fig 

 condition of cleistogamy is found in 

 the earlier-flowering plants, so that it is probably a mere 

 result of check through a colder temperature. 



Salvia clandestina may be compared with the last 

 described, as it is a self-fertilising form of, perhaps, S. pra- 



l c 



a, Cleistogamous flower- 

 bud of Lainium aiitplexicaule; b, 

 vertical section of same ; c, pistil. 



59.- 



