Dr Stopes[67] regards the integument as double in origin, a view suggested by Griffith[68] in 1835, and as homologous with the single integument _plus_ the cupule of _Lagenostoma_. This view is supported by Mrs Thoday[69]: on the other hand Miss Kershaw’s investigation of _Bowenia_ seeds leads her to regard the integument as single. Although there would seem to be a _prima facie_ case in favour of the dual nature of the integument, the arguments on the other side have greater weight[70]. [Illustration: Fig. 396.] [Illustration: Fig. 396. A. Seed of _Dioon edule_ in longitudinal section; _a_, integument; _v_, vascular tissue; _m_, prothallus; _n_, nucellus; _p_, pollen-chamber; _s_, absciss-layer; _ar_, archegonia. (After Chamberlain.) B, B′. Seed of _Cycas circinalis_; _a_, _v_, integument (sarcotesta) and vascular tissue; _b_, sclerotesta; _c_, inner sarcotesta; _m_, _n_, prothallus and nucellus. (After Stopes.) B′. Apex of nucellus; _p_, pollen-chamber; _i_, integument; _n_, nucellus; _ch_, archegonial chamber; _ar_, archegonia. C, D. Seed of _Encephalartos Altensteinii_; C, surface of stone. (After Stopes.) E. Stem of _Bowenia serrulata_; _g_, level of ground. (After Chamberlain.) F, F′. Pinnae of _Macrozamia heteromera_. G. Pollen-tube of _Microcycas Calocoma_. (After Caldwell.) H. Transverse section of stem of _Encephalartos horridus_; _s_, stele; _g_, girdle-bundles. (After Mettenius.) I. Apical view of prothallus of _Cycas_ showing two archegonial chambers (_ch_). (After Treub.) K. _Encephalartos Barteri._ Transverse section of stem; _x_, xylem; _p_, phloem. (After Matte.) L. _Cycas siamensis._ Transverse section of vascular tissue of young stem. (After Matte.) M. _Cycas revoluta_; two motile sperms. (After Miyake.) N. Long hair with short basal cell from the petiole of _Macrozamia heteromera_. (After Robertson.) O. Vascular bundle of _Dioon edule_ from base of petiole; _p_, phloem; _c_, cambium. (After Mettenius.)] Recent observations point to the probability that insects play a part in the pollination of cycadean ovules. Kraus[71] drew attention to the strong smell emitted by the microstrobili of _Dioon edule_ and noticed that small bees were attracted to the ripe strobili of _Macrozamia_, while odourless cones of a neighbouring _Ceratozamia_ received no attention. Pearson[72] and Rattray[73] have obtained evidence that beetles and weevils act as pollinators to species of _Encephalartos_.