Experiments show that insects can function as pollinators of cycads, rare, palmlike tropical plants. Furthermore, cycads removed from their native habitats—and therefore from insects native to those habitats—are usually infertile. Nev- (5) ertheless, anecdotal reports of wind pollination in cycads cannot be ignored. The structure of cycads male cones is quite consistent with the wind dispersal of pollen, clouds of which are released from some of the larger cones. The male cone of Cycas circinalis, for example, sheds almost (10)100 cubic centimeters of pollen, most of which is probably dispersed by wind. Still, many male cycad cones are com- paratively small and thus produce far less pollen. Further- more, the structure of most female cycad cones seems incon- sistent with direct pollination by wind. Only in the Cycas (15)genus are the females’ ovules accessible to airborne pollen, since only in this genus are the ovules surrounded by a loose aggregation of megasporophylls rather than by a tight cone.
24.According to the passage, the size of a male cycad cone directly influences which of the following? (A) The arrangement of the male cone’s structural elements (B) The mechanism by which pollen is released from the male cone. (C) The degree to which the ovules of female cycads are accessible to airborne pollen (D) The male cone’s attractiveness to potential insect pollinators (E) The amount of pollen produced by the male cone
25. The passage suggests that which of the following is true of the structure of cycad cones? (A) The structure of cycad cones provides conclusive evidence in favor of one particular explanation of cycad pollination. (B) The structure of cycad cones provides evidence concerning what triggers the first step in the pollination process. (C) An irresolvable discrepancy exists between what the structure of most male cycad cones suggests about cycad pollination and what the structure of most female cones suggests about that process. (D) The structure of male cycad cones rules out a possible mechanism for cycad pollination that is suggested by the structure of most female cycad cones. (E) The structure of male cycad cones is consistent with a certain means of cycad pollination, but that means is inconsistent with the structure of most female cycad cones.
26. The evidence in favor of insect pollination of cycads presented in lines 2-4 would be more convincing if which of the following were also true? (A) Only a small variety of cycad species can be successfully transplanted. (B) Cycads can sometimes be pollinated by means other than wind or insects. (C) Insects indigenous to regions to which cycads are transplanted sometimes feed on cycads. (D) Winds in the areas to which cycads are usually transplanted are similar to winds in cycads’ native habitats. (E) The transplantation of cycads from one region to another usually involves the accidental removal and introduction of insects as well.
27. The passage suggests that which of the following is true of scientific investigations of cycad pollination? (A) They have not yet produced any systematic evi- dence of wind pollination in cycads. (B) They have so far confirmed anecdotal reports con- cerning the wind pollination of cycads. (C) They have, until recently, produced little evidence in favor of insect pollination in cycads. (D) They have primarily been carried out using cycads transplanted from their native habitats. (E) They have usually concentrated on describing the physical characteristics of the cycad reproductive system.