The efficiency of pollen transfer and rates of embryo initiation in Cryptantha (Boraginaceae).

The efficiency of pollination and rates of embryo initiation were compared in two species of Cryptantha (Boraginaceae) which differ greatly in their patterns of seed (nutlet) production. Cryptantha flava normally matures only one of the four ovules per ovary while C. flavoculata often matures all four. The general floral morphology and composition of insect floral visitors were found to be nearly identical in the two species, but C. flavoculata produces twice as much pollen per flower as C. flava. Despite this difference, the amount of pollen deposited on stigmas by pollinators is similar. This may be due to the larger stigmatic surface area in C. flava. In both species, the abortion of fertilized ovules, rather than insufficient amounts of pollen, appears to be the primary factor regulating the number of seeds per flower. The pollination ecology of these species is discussed in relation to current theories regarding the allocation of resources to the production of pollen and seeds.