310 Wilhelm Bock 1969
The most outstanding trait of the microstrobilus is its resemblance with that of the living Araucaria muelleri, both having this organ basally surrounded by a pericone, consisting of several whorls of ovate, protective leaf scales. They rather abruptly yield to the armor of tightly set, roundish oval to rhomboid, slightly imbricate microsporangia, which represent those more articulate, stalked sporophylls, known in related, living araucarians (fig. 541). On the outside these convex scales have a weak bilateral aspect, strongly impressed by two pointed, distal tips, which clasp the scale above. The paired tips remind of the single dichotom, known in the ancient coniferous leaves such as Lebachia, while the lower surface of the scale is partially grooved and ridged. The interior of the scale is shown in fig. 541. The pericone leaves (fig. 536-537) are obovate to club-shaped, the larger ones being quite thick, caused by a narrow lens-shaped cavity. A rather thick, stringy axis is exhibited in fig. 541, occupying about a quarter of the cone diameter. The pericone is about twice as wide as the somewhat tapering microsporophyll section above it.
The most prominent pattern of the macrostobilus is the prolific arrangement of the tightly squeezed rhomboidal apophyses, which in most cases is all that the cone seems to represent. In spite of their intricate design, the shielrls apparently lack sufficient morphological and genetic clues, being generally mostly treated as a scale terminal or protective character. Its structural extension into the scale is also little explored. The employment of an apophysis in the conifers, just as in the cycads, may vary from one genus or species, to another, being now prominent and again suppressed. The living genus Picea possesses just useful shaped, imbricate, smooth, scales, while Pinus exhibits an apophysial armor, which causes at some growing stages marginal pressure with such strength that they hardly can be pried open, representing a most effective closed container. The polarity of the apophysis to the cone, or the scale axis, varies also successively. While the position of the seed scales in reference to the cone axis, such as in Pinus nigra, is about 90 degrees at the base, it gradually changes to about 45 degrees, slowly increasing its angle until it is zero at the apex of the cone. The phase of the apophysis could be expected to be rectangular to the scale axis. In Pinus it is presently placed largely parallel to the upper outside of the scale, securing the lock-like, surface position by the varying steep angle of the scale axis to the cone stem axis. It appears that the apophysis in Pinus is entirely a part of the seed, or sterile scale, as the bract scale in this genus was already phylogenetically suppressed. However, Florin (1944), Strassburger (1872;) Hagerup (1933) and others do not fully agree in their opinion about the ontogenetic development of the bract and seed scale, and it is difficult to judge from often incomplete fossil material the phylogenetic trend in related groups. Florin (p. 546) postulates that two transverse sterile scales placed above the seed scales are preferably forming his seed scale complex. In Pinus nigra I found that the macrosporangium displays a short, stalk-like attachment, about 1 mm wide, to the cone axis, segregating peripherally about 18 vascular bundles, spreading fan-like into a quite thin, gradually broadening, more or less two-sectional scale on the
Fig. 528 - Primaraucaria wielandi Bock. Primary branch with overlapping paired scales.
Fig. 528A - Enlargement of fig. 528.
Upper Triassic, Winterpock, Virginia; spec. 3101, x 2.
Fig. 529 - Primaraucaria wielandi Bock. Tip of shoot. Upper Triassic, Winterpock, Virginia; spec. 3120, x 1.
Fig. 530 - Primaraucaria wielandi Bock. Shoot on pericone. Upper Triassic, Virginia.
Fig. 531 - Primaraucaria wielandi Bock. Enlargement of scale leaves with wrinkles; spec. 3123, x 2 (in Bock, 1954).
Fig. 533 - Primaraucaria wielandi Bock. Apophyses; spec. 3151, x 2 (in Bock, 1954).