i24 THE CHEMICAL EXAMINATION OF MACROZAMIA SPIRALIS. Bv James M. Petrie, D.Sc, F.I.C, Linneax Macleat Fellow op the Society in Biochemistry. (From tlte Plii/siological Laboratory of the Universiti/ of Sydney.) Historical Importance, and Distribu tion of Cycads 424 Record of their poisonous Character • . . . 425 Experimental Work on 3/itrro:tiiiii(i spiralis : Proximate Composition of leaves and nuts 429 Complete Chemical Examination 431 Feeding Experiment;: 439 Summary 440 Historical. — The family of the Cycadaeeae are all tropical or subtropical plants. The genera have a very limited distribution, and are few in number, but these represent the remnants of a once extensive flora which covered the earth in the Palaeozoic and Mesozoic Eras. Scott, in his "Evolution of Plants," says that in the Secondary Floras al)out one plant in every three was a Cyead, and they stretched from the Equator to the Poles. They were the dominant class; there was nothing above them: they were the best thing in the way of flowering plants that their age had produced. Though these in giving rise to the Angiospei'ms gradually became extinct, yet from some less progressive and therefore less highly organised cycadeau forms, we may trace through the Tertiary Era the plants which linger on to our present day. In the descendants of this ancient race of jilants we still find those primitive functions and primitive structures which closely resemble those indicated in the fossils of the Carboniferous Period, and which give to the Cycads a history and an interest uni(|ue among plants. The fossil cycadj make their first appearance with the genus PterophyUnm in the Upi^er Carboniferous formations, and reach their maximum towards the end of the Triassic and the beginning of the Jurassic Periods. Of these ancient forms Schimper recognised 34 genera which include 278 species. Distribution. — The Cycadaeeae of the present day, according to Engler and tlie Index Kowensis, include mdy nine genera and 75 species. Four genera, in-cluding Zanria, belong to tropical America, two are confined to the African con-tinent, and three are found in Australia. The last include Cyca^ which is widely distributed from India to Japan and through the Islands to Australia, oiu^ Queens-land genus, and 'Macror:amia whicli is limited to Australia.