GYMNOSPERMA E. CYC A DEA E. 



315 



which reach the considerable size of a mature medium-sized plum before fertilisation ; 

 the ripe seed, the altered macrosporangium now containing the macrospore, has the 

 size and appearance of a middle-sized apple hanging naked on the carpel. The 

 numerous leaves of the male flowers that bear the microsporangia, the staminal leaves, 

 are much smaller, seven or eight centimetres in length and not divided, becoming 

 broader above from a narrower base and pointed ; on their under side are sori of 

 many microsporangia ; the whole flower is from thirty to forty centimetres in length. 



The male and female flowers of the other genera of the Cycadeae are not unlike 

 fir-cones in outward appearance ; 

 on a short naked stalk rises like 

 a spindle the comparatively slender 

 floral axis bearing numerous closely 

 crowded leaves with macrospo- 

 rangia or microsporangia (Fig. 

 247), and ending above in a naked 

 apex which has ceased to grow 

 (Fig. 247 D). The staminal leaves 

 are small indeed in comparison 

 with the foliage-leaves of the same 

 plants, and yet they are about the 

 largest and most massive to be 

 found in Seed-plants ; in Macro- 

 zamia, as in Cycas, they are from 

 six to eight centimetres long and 

 may be three centimetres broad; 

 they are narrow at the point of 

 insertion, expand into a kind of 

 lamina, and are simply acuminate, 

 as in Macrozamia, or divide into 

 two hooked points, as in Ceraio- 

 zamia ; or again the lower part is 

 slender like a stalk and bears a 

 shield-like expansion (Zamia]. The 

 staminal leaves of the Cycadeae 

 are also distinguished from those 

 of most other Seed-plants by their 

 persistence ; they become lignified 

 and often very hard. The numerous 

 microsporangia (pollen-sacs) on the 

 under side of the staminal leaves are usually collected together into small groups of 

 two to five sporangia each, resembling the sorus of the Ferns ; these in their turn 

 form larger groups on the right and left side of the leaf. The pollen-sacs are round 

 or ellipsoidal, usually about one millimetre in diameter, and are attached to the under 

 side of the staminal leaf by a narrow base, which in Zamia spiralis according to 

 Karsten becomes a stalk; they open by a longitudinal fissure. 



The development of the microsporangia and of the leaves that bear them is most 



FIG. 246. A fertile leaf (carpel) of Cycas revoltita about half the natural 

 size ;./"the lobes of the carpel which resembles a foliage leaf, sk ovules in 

 the place of the lower pinnae, sk' a more highly developed ovule. 



