330 FOURTH GROUP. SEED-PLANTS. 



in a stellate manner at the time of flowering; in the former species the ovules or 

 macrosporangia are placed in pairs in the axils of the lower scales to the right and 

 left of the median line, and are seldom abortive. Callitris has more than two, 

 usually three ovules in the axils of the outer scales (Fig. 258), the upper pair being 

 either sterile or having only a few ovules. In Cupressus the number of ovules at 

 the base of the scales is still larger. The fruits of Arccuthos drupacea and Frenela 



verrucosa in the collection at Wiirzburg 

 consist of alternating whorls of scales 

 each containing three members, which 

 open in the latter species after the 

 seeds are ripe, like a six-valved cap- 

 sule ; in this case the inner side of 

 try a i >^ \ each scale is swollen up into a thick 



Xs ^^gg|gg_ \ 



placenta ascending from the base to 



FIG. 258. Callitris quadrvvalvis. A the female flower, magnified ; 



dd two pairs of decussate leaves (the carpels) with six ovules Ks in their the 3,peX and bearm " nUmerOUS will"ed 

 axils. B an ovule in vertical longitudinal section through its broader 



diameter; A'A' the nucellus still without an embryo-sac, i the integu- SCedS diSpOSed thrC6 Side by side in 

 ment prolonged into a tube with the micropyle m. 



a transverse row ; there are from four 

 to six rows in each carpel, the entire inner surface bearing seeds nearly to the apex. 



In the last group also, the Taxineae, the macrosporangia (ovules) are formed 

 both on leaves and in the axils of leaves. The first kind occurs in a very remarkable 

 form in the Tasmanian genus Microcachrys. The scales of the cone bear their 

 solitary macrosporangium so near the upper end of the inner surface (Fig. 256, 5), 

 that it projects between the summits of the scales ; in Dacrydium it is placed on or 

 even below the middle of the scale, and in this genus no cone is formed, the scales 

 simply standing singly or two together at the extremity of a branch. In both genera 

 the macrosporangium is surrounded when the seeds are ripe by the integument 

 and by an outer envelope, which is still quite short in the flowering time but after 

 fertilisation grows into a cup-shaped fleshy brightly coloured structure, the aril, a 

 formation which is generally characteristic of the Taxineae, but is absent in Cepha- 

 lotaxus and Gingko. In the peculiar genus Podocarpus the aril is present as early 

 as the flowering time in the form of a second outer integument, which makes its 

 appearance after the proper inner integument. In Podocarpus dacryoides the ovule 

 is inverted (anatropous), and grows on the inner surface of a scale (Fig. 256, 9) im- 

 mediately beneath the apex, adhering to it along its whole length. In other species 

 of Podocarpus the position is somewhat different ; the macrosporangium has the 

 form of the anatropous ovule in the Angiosperms, and does not adhere to the 

 scale. The small flowering shoots proceed in P. chincnsis from the axils of 

 foliage-leaves, in P. chilina from the axils of minute scale-leaves at the end of 

 elongated leafy shoots, and consist of an axis which is slender and stalk-like 

 below and enlarged and angular above, and bears three pairs of very small de- 

 cussate scales. Usually only one scale of the second pair is fertile, and bears the 

 anatropous macrosporangium on its inner surface with the micropyle directed down- 

 wards towards the apex of the contracted flowering shoot. The leaves of the shoot 

 in many species unite together to form a fleshy body, the so-called ' receptacle.' In 

 Phyllocladus the lower lateral members of the shoot-system with its bilateral and leaf- 

 like branches are changed into female flowers, which are raised on a stalk and are 



