338 Dr. D. H. Scott [May 15, 



In the genus Stangeria from tropical Africa, the leaves bear so 

 close a resemblance to those of some Ferns in form and veining, that 

 the plant, before its fructification was known, was described by com- 

 petent botanists as a species of the Fern genus Lomaria. 



In all Cycads the male fructifications are in the form of cones ; 

 the pollen-sacs are borne in great numbers on the under surface of 

 the scales of the cone. In all the genera but one, the female 

 fructifications are also cones, each scale bearing two large ovules. 

 In the type genus Cycas, however, there is no sj)ecialised female cone 

 at all, the fertile leaves are borne in rosettes on the main stem, 

 a,lternating with zones of the ordinary vegetative leaves. 



The fertile leaves are of large size and compound form, and 

 usually each of them bears several ovules, which, whether fertilised 

 or not, grow to a great size, sometimes as big as an egg-plum. They 

 are in some species of a bright red colour, and, contrasting with the 

 yellow woolly leaves on which they are borne, are conspicuous and 

 beautiful objects. 



In thus bearing its seeds on leaves so little modified and springing 

 like the ordinary leaves from the main stem, Cycas is the most fern- 

 like genus of Flowering plants. 



The ovule, at the time when pollination takes place, is about the 

 size of a small hazel nut. It consists of an outer envelope and a 

 central body, the two being closely joined together, except towards 

 the top, where the envelope leaves a narrow passage open, leading 

 down to the central body. The apex of the latter becomes excavated 

 into a hollow pit, the pollen-chamber, a feature almost peculiar to 

 Cycads amongst living plants, discovered by our countryman GrifSth 

 as long ago as 1854,* though the credit is olten wrongly given to later 

 French or German investigators. 



The pollen, blown by the wind or possibly conveyed by insects, 

 is received in the opening of the envelope by a drop of gummy 

 substance, and as this evaporates, the pollen-grains are drawn down 

 through the narrow passage into the pollen-chamber below. There 

 each grain anchors itself by sending out a tube into the neighbouring 

 tissue of the ovule ; thus pollination is accomplished. Fertilisation, 

 i.e. the actual union of the male and female cells, takes place some 

 months later, when the ovule, now to all external appearance a seed, 

 has reached its full size. In the meantime, the single megaspore or 

 embryo-sac, imbedded in the tissue of the central body cf the seed, 

 has prown to enormous dimensions, filled itself witli prothallus and 

 developed the egg-cells at its upjier end, which are so large as to be 

 easily seen with the naked eye. 



The pollen-grain behaves like a cryptogamic micrdspore and 

 develops two large spermatozoids each with a spiral band bearing 

 numerous cilia — the organs of motion. The pollen-tube becomes 



* Iccnes Plant. Asiat., Part iv.. Plates 377 and 378; Notula) ad Plant. 

 Asiat., pp. 6-8. 



