228 ßryophyten. — Pteridophyten. 



arbeitung der Gattung Calymperes in seinem Werke über die aus- 

 sereuropäischen Laubmoose zugrunde gelegt werden soll. 



L. Loeske. 



Williams, R. S., Trichodon borealis n. sp. (Br)'olocnst. XIV. p. 5. 

 pl. 2. January, 1911.) 



Description and illustration of Trichodon borealis Williams sp. 

 nov., the type specimens from Dawson, Yukon Territory, Williams, 

 July 9, 1899. The new species is compared at length with T. cylin- 

 dricus and its nearer ally T. oblotigus. Maxon. 



Bower, F. O., On the primary xylem and the origin of 

 medullation in the Ophioglossaceae. (Ann. Bot. XXV. p. 537 — 

 553, pl. XLV, XL VI. 1911.) 



It was found that the absence of the protostelic stage in the 

 ontogeny of the vascular system of the young plant depended on a 

 relatively large supply of nourishment. In weak plants of Botrychium 

 lunaria the stele may at first be protostelic or may contain but a 

 few scattered parenchymatös cells. In both cases an intrastelar pith 

 arises at the level of the first leaf trace; in the latter case it arises 

 by the concentration of the parenchymatös cells. The ring of xylem 

 opens before the departure of the trace, the xylem of which comes 

 off from one of the free edges; and the pith comes into connection 

 with the intrastelar but extraxylic parenchyma of the xylem sheath. 

 The ring closes again and the stele may once more become proto- 

 stelic except for the presence of a few scattered parenchymatös cells. 

 Before the departure of the next trace the ring of xylem opens again 

 and these processes may be repeated at the exit of the later traces. 

 In all these cases the endodermis is unbroken at the departure of 

 the foliar bündle, for it forms two involutions that meet as the lat- 

 ter moves outwards; in one plant a band of endodermis appears as 

 a new formation rather than as an involution before the outer endo- 

 dermis is broken. But in neither plant was there any indication at 

 the departure of the early traces of any continuity of cortex and 

 pith. As the leaves become larger the involutions of the endodermis 

 become more marked. At the departure of later leaves the endodermis 

 is broken; but this is held to be "plainly the result of that imper- 

 fect formation of the endodermal characters which is general in the 

 older regions of these plants". The fading out of the endodermal 

 characters may be traced as we pass upwards and it begins exter- 

 nally to the trace itself. Thus the pith is at first intrastelar, but in 

 older leaves extrastelar additions to it may be made by the intru- 

 sion of foliar pockets; the parenchyma associated with the leaf trace 

 is at first separated by the endodermis from the already existent 

 pith, but as the plant becomes established the endodermal barrier 

 between the components of the pith is not maintained. Thus the pith 

 is primarily but not wholly intrastelar in origin. In Botryclüum Iwiaria 

 there is much more primary xylem than in B. virginianum ; even in 

 the latter where the primary xylem is virtually absent isolated internal 

 tracheides occur though very rarely and can hardly be any thing but 

 vestigial primary xylem. A wounded specimen of Botrychium ternatitm 

 shovved internal tracheides in the damaged region, though none were 

 observed elsewhere; this fact is regarded as signilicant in view of 

 Jeffrey's conclusion that traumatic changes are apt to be reversionary. 



Isabel Browne (Universty College London). 



