5^8 PHANEROGAMS. 



above the ground, and is broad above with a furrow across the top, while it is 

 tuberous below, and passes into the tap-root \ 



The Flowers of Gnetaceae are unisexual, and are arranged in dioecious 

 {Ephedra) or monoecious inflorescences ; the inflorescence has a well-defined form, 

 and in Ephedra and Gnetum springs from the axils of the opposite leaves. The 

 male flower of these genera consists of a small bifid perianth, in the middle of 

 which rises a staminal column, which in Gnetum is bifurcate above and bears two 

 bilocular anthers, in Ephedra a larger number crowded into a head. The female 

 flower oi Gnetum (Eichler, in Flora 1863, p. 463), like that oi Ephedra, also possesses 

 a perianth, flask-shaped in the former, obscurely trigonous in the latter genus ; it 

 envelopes a central ovule possessing in the case of Ephedra one integument, in 

 that of Gnetum two, the inner of which is elongated like a styled The more exact 

 morphology of these flowers is still doubtful. In Gnetum the inflorescence, which 

 springs from the axil of the foliage- leaves, consists of a jointed axis with verticillate 

 leaves, in the axils of which the flowers, male and female, are agglomerated. The 

 inflorescence of Welwitschia'^ is a dichotomously branched cyme nearly a foot in 



^ For a full description of this remarkable plant see J. D. Hooker in Trans. Linn. Soc. 

 vol. XXIV. 



"^ [According to Beccari (Delia Organogenia dei fiori feminei del Gnetum Gnemon, Nuovo 

 Giorn. bot. ital. IX, 1877) the female flowers are lateral axes, the nucellus being the end of the axis. 

 Strasburger (Angiospermen und Gymnospermen) regards the two investments of the nucellus in 

 Ephedra and the three in Gnetum as integuments.] 



3 [According to Professor W. R. M^Nab, 'The cones of Welwitschia consist of numerous 

 opposite and decussate bracts, with a sessile flower in the axil of each of the bracts. The perfect 

 flowers in the male cone consist of two outer perianth leaves (calyx) placed right and left, two inner 

 ones (corolla) placed anteriorly and posteriorly, six stamens united below, and two carpels anterior 

 and posterior, the conical end of the axis projecting as a rudimentary axile ovule surrounded by the 

 two carpels. The outer parts of the perianth are first developed appearing as two shoulders at the 

 very base of the young floral branch. The flower next in age has the floral axis more elongated, the 

 outer parts of the perianth larger, and a distinct swelling is visible above the outer parts. These 

 swellings are anterior and posterior, and much larger than the outer parts. Above the inner parts of 

 the perianth the axis is expanded, and contracts near the rounded apex. The expanded portions are 

 superposed on the outer lateral parts of the perianth, and are the two primordial staminal cushions. 

 These cushions are semilunar, and in the earlier stages show no trace of division into three. At this 

 stage the parts of the perianth rapidly enlarge and cover in the central parts of the flower. A pro- 

 jection now forms anteriorly and posteriorly, the first indication of the two carpels. The next stage 

 shows the two staminal cushions each forming three elevations, the central one larger than the two 

 lateral ones.- The six stamens are thus produced by the branching of two primordial stamens. In 

 the next stage the carpels elongate and cover in the punctum vegetationis, ultimately developing 

 the peculiar style and stigma-like process. The axis elongates slowly and forms a conical pro- 

 jection which is undoubtedly a rudimentary axile ovule, but it never shows any appearance of 

 an embryo-sac.' 



In the female flowers, which are produced in different cones from the male flowers, the develop- 

 ment is very different. A very short stalk is developed in the female, which is wanting in the male ; 

 then two shoulders are developed exactly like the two outer parts of the perianth in the male flower, 

 to which Dr. Hooker considered them to be equivalent. Judging from the construction of the male 

 flower. Professor M'^Nab was disposed to accept this view; but with hesitation, as he could not 

 account for the stalk-like process. Strasburger however concludes that they are carpels, and in 

 that M'^Nab quite concurs. Above the carpels the axis elongates slightly, and a ring is formed 

 surrounding the punctum vegetationis. This ring is the ovular integument. Comparing the two 

 flowers, it will be seen that in the male there are four series of parts, in the female the three outer 

 series are wanting and only the carpels remain. But in the male flower the carpels are anterior and 



