

I909 j CURRENT LITERATURE 245 



described Physostoma elegans from the Lower Coal-measures, but a little later 

 placed it in his new genus Lagenostoma as L. physoides. Oliver now proposes 

 to revive the genus Physostoma as distinct from Lagenostoma, replacing the 



nam 



L. Kidstonii as P. Kidstonii. 



6 mm ) 



Physostoma elegans is remarkable in several particulars. It is a small (5.5- 



of the nuceUar beak, as in Lagenostoma; but in this free region the integument 

 consists of ten distinct lobes ("tentacles" the author calls them). These lobes 

 are the direct prolongation of the ribs below, and represent the units of the "canopy" 

 of Lagenostoma. Both lobes and ribs are clothed with long, club-shaped hairs. 

 The testa shows no stony layer, and therefore is homogeneous, consisting of five 

 or six layers of close-fitting, thin-walled, elongated cells. The vascular system 

 enters the narrowed base of the seed as a single strand, which at once breaks up 

 bto a ring of strands, each one of which traverses a rib and continues on through 

 the corresponding free lobe . The vascular strands lie along the inner limit of 

 the integument, in what would be the "inner fleshy layer" had the usual three- 

 layered differentiation of the testa occurred. On the outside of each strand there 

 is a lacuna ; and in the base of the seed a continuous lacuna surrounds the single 

 large strand and the group of separating strands. It is suggested that these lacunae 



represent the position of disorganized phloem. 



The nucellus is remarkable in its peripheral "secretory zone," which extends 

 from the chalaza to the tip of the nucellar beak. The "secretory sacs' are thin, 

 oblong, tabular cells, separated by a tissue of smaller cells. They are most abun- 

 dant and crowded in the funnel-shaped region of the chalaza bounded by the mer- 

 ging vascular strands and the base of the embryo sac. The author sees m 

 presence of these secretory sacs the retention in the ovule of a feature presen r 

 the vegetative organs, in which character Physostoma is unique in the Lage^ ^ 

 stoma group. Between the secretory zone and the sac there is a tissue ^0 ^^ 

 more radially compressed layers, which the author calls the ' ' tapetum. ^ 



this may represent the active nutritive zone developed in many gymnospe 

 m the nucellar tissue surrounding the sac; or it may be the ordinary nuceUa 

 sue compressed by the enlarging sac. The megaspore membrane was on 

 Anally detected, and then as a very delicate one. The pollen chamber asm 

 T,^... . \ _ _ * . . ., :j~^; c nf the nucellar oeak 



formed bv the separation of the epidermis 



v_, ^^ 10 luiincu uy uie seua.iat,i<uFii vx ■-«- -r~ . ^na into 



*">* the subjacent tissue, giving the appearance of nucellar tissue grcn ing m 

 ^ pollen chamber as a conical mass, the chamber thus becoming a beiw ^ 

 c *vke. Physostoma differs, however, from Lagenostoma, in the lac ^ 

 embryo sac invades this hpat sn that the aoex of the sac is invested oy 



bottle"). Oliver 



~v puuen cnamber ("like the incurved dohuw u» » - , {( ■ 



suggests that this apical prolongation of the sac of Physostoma may be P 



mordial tent pol 



which show 



The pollen chambers contain an abundance of pollen grams, w 

 ** ceu-c 0m pie X now known in several paleozoic seeds. The author thinks 



