48 SCIENCE PROGRESS. 



elements, except at the auriculate swellings where its thick- 

 ness increases. This sheath of tracheal elements occurs, 

 therefore, between the radially arranged tracheids of the 

 secondary xylem and the central axis of the stem ; its 

 tracheae are distinguished from those of the secondary 

 xylem by a scalariform pitting and larger diameter. 



By an examination of a series of transverse and longi- 

 tudinal sections, Solms made out that from the two ends 

 of the major axis bundles of primary tracheae become de- 

 tached from the elliptical sheath, and pass off to supply 

 certain lateral appendages arranged alternately in two 

 vertical rows. The conclusion is arrived at that the ap- 

 pendages are of the nature of leaves, and, in the stem 

 sections described, the scars left by the fallen leaves have 

 been completely covered over by a development of second- 

 ary wood subsequent to the leaf-fall. The cortex is rarely 

 preserved ; the plane of the Cambium in one of the figured 

 sections being occupied by a layer of calc-spar ; externally, 

 the Cambium is followed by alternating bands of pitted 

 sclerenchymatous tissue and crushed thin-walled elements, 

 probably representing bands of hard and soft bast ; the 

 thick-walled cells are, however, isodiametric and not fibrous 

 in form. 



In speaking of the affinities of this plant the author of 

 the paper naturally lays stress on the primary tracheal 

 sheath as a character which at once separates Protopitys 

 from Gymnosperms and Calamariece ; on the other hand, 

 it shows a resemblance to such plants as Sigillaria and 

 Lyginodendron, especially Lyginodendron Oldkamium Will. 

 The differences between Protopitys Buchiana Goepp. and 

 Lyginodendron Oldkamium are sufficiently numerous to 

 warrant the institution of a new family, the Protopityece. 

 The sole representative genus affords another example of a 

 synthetic type of plant in v/hich there appear characters 

 intermediate between the Filicinece and Gymnosperms, 

 indicating the descent of these two classes of plants from 

 an original ancestral group. 



Passing to Upper Carboniferous times there are several 

 contributions to be noticed of exceptional interest. 



