but carry pollen in masses called "pollinaria" so the many thousands 

 of ovules per capsule are fertilized at once. Variation in seed 

 production is conditioned by the effectiveness of the pollinators, as 

 well as by the physiological state of the plant. 



b. Seed viability and longevity: Seeds of orchids are very short-lived, 

 with an undifferentiated embryo and little or no endosperm (Cronquist 

 1968). They have limited time span for germination after seeds 

 dehisce and are generally considered to require endomycorrhizae to 

 germinate in the field (Wells 1981). 



c. Dormancy requirements: Seeds of orchids lack carbohydrate storage 

 and thus lack the capacity for seed dormancy. 



d. Germination requirements: Orchids seeds are very small and 

 require a narrow range of moisture and temperature conditions to 

 germinate. It is likely that they require direct contact with the mineral 

 substrate. 



e. Percent germination: Unknown. 



5. Seedling ecology: Orchid seedlings are usually unable to continue growth 

 without endomycorrhizal symbionts, the hyphae of which usually enters 

 through the suspensor end to penetrate the germinating embryo (Dressier 

 1990). Species of Spiranthes initially become established as saprophytic, 

 underground plants, dependent on the fimgi for carbohydrates as well as 

 nutrients and water. The ensuing underground stage is reported to last for 8 

 years in Spiranthes spiralis until a vegetative shoot is produced, and flowers 

 are not produced until 13-14 years after germination (Wells 1967). By 

 contrast, green leaves are produced in 2 years after germination by S. 

 honkonganense (Sun 1 995). 



6. Survival and mortality: Stochastic and deterministic modeling of the 

 monitored populations in Colorado and Utah projected population extinction 

 for almost all of the populations under most agricultural practices except the 

 "grazed only" population segment and to a lesser extent the "twice clipped" 

 population segment under the deterministic model; and the urmianaged 

 riparian populations under both the deterministic and stochastic models (Arft 

 1995a). 



Species' longevity and the primary causes of mortality are unknown. The 

 mean life span expectancy oi Spiranthes spiralis plants studied by Wells 

 (1967) was calculated to be more than 50 years. 



37 



