 Trillium grandiflorum has long been thought to self @-@ pollinate based on the fact that pollinators had rarely been observed visiting the plants and because there is low variation in chromosomal banding patterns . This has been strongly challenged , as other studies have shown high pollination rates by bumblebees and very low success of self @-@ pollination in controlled experiments , implying that they are in fact self @-@ incompatible . Several ovules of a given individual often fail to produce seeds . One contributing factor is pollen limitation , and one study showed that open pollinated plants had 56 % of their ovules produce seeds , while in hand pollinated individuals the figure was 66 % . Plants with reduced exposure to pollinators were 33 % to 50 % less likely to produce fruits than those that were , while hand pollinated individuals showed a 100 % fruit set ( though these fruits did not contain a 100 % seed set ) . Plant resources were shown to be a limiting factor in seed production : when pollen was in abundance , larger plants had a significantly greater seed to ovule ratio than smaller ones . The overall suboptimal seed to ovule ratios suggest that Trillium grandiflorum has evolved to maximize reproductive success in the face of highly stochastic pollination , where some plants may only be visited by a single pollinator in a season . 
