CONIFERM. 



451 



The ovules of Junipenis communis (Fig. 319, C) stand in whorls of threes 

 beneath the naked extremity of the floral axis, the flower springing as a litde 

 shoot from the axil of a foliage-leaf, and its axis bearing whorls of three leaves. 

 The ovules apparently alternate with the three leaves of the upper whorl, and 

 hence must, from their position, be themselves considered as metamorphosed 

 leaves ; these leaves of the upper whorl swell after fertilisation, grow together 

 and become fleshy, forming the pulp of the juniper-berry in which the ripe seeds 

 are entirely enclosed ; they may therefore be termed carpels. In the other Cupres- 

 sinese the flower consists of decussate whorls of two or three leaves, which grow 

 considerably after fertilisation and attain a considerable size, enveloping the seed 

 and forming a pericarp which may therefore correctly be said to be formed of 

 carpels. In Sabina the pericarp is fleshy and berry-like, as in Juniperus; in the 

 other genera, on the other hand (Thuja, Cupressus, Callitris and Taxodium), 

 the carpels become woody artd assume the form of stalked peltate scales, or of 

 valves separating from one another longitudinally (Frenela) ; these are closely 

 approximate during the development of the seed, but afterwards open to allow 

 the ripe seeds to fall out. The erect ovules of Cupressinese sometimes appear 

 to stand in the axils of the carpels; but it is clear in other cases that they 



Fig. yi-i— Callitris quadrivalvis ; A female flower (mafi:nified) ; d d two pairs of decussate leaves (carpels) in 

 tlic axils of which are six ovules (A V) ; B vertical longitudinal section of an ovule through its broader diameter; 

 A' A' the nucleus still without an embryo-sac ; i the tubular elongated integument with the micropyle m. 



spring from the carpels themselves, either low down near their point of insertion 

 or at a greater height. In Sabina and Callitris quadrivalvis (Fig. 322) only two 

 decussate pairs of carpels separate like a star at the time of flowering; in Sabina 

 the ovules stand in pairs in the axils of the two lower carpels, right and left of 

 their median line, some of them being frequently abortive. In Callitris quadri- 

 valvis a pair occurs on each of the lower carpels and a pair higher up; but this 

 position can only be explained by further investigation of the history of their 

 development. In Thuja and Cupressus there are three or four decussate pairs of 

 carpels, in Taxodium a still larger number; in Thuja and Taxodium two erect 

 ovules are situated at the base of each of the central pairs of carpels, springmg 

 from the right and left of their median line ; in Cupressus there are a considerable 

 number at the base of each carpel. In Juniperus drupacea and Fretiela verrucosa 

 the fruits (in the collection at Wiirzburg) consist of alternating whorls of three 

 carpels, opening, in the last species, after the seeds become ripe, like a six-lobed 

 capsule. Each carpel is swollen on its inner side into a thick placenta ascending 

 from the base to the apex, and bearing numerous winged seeds which stand in 

 transverse rows of threes ; there are from four to six of these rows on each carpel, 

 the whole inner side therefore bearing seeds nearly up to the apex. 



Gg 2 



