1888. | BOTANICAL GAZETTE. 43 ais 
A monograph on Stigmaria.‘ pes.” 
Professor Williamson has done more, probably, than any other indi- & 
vidual towards perfecting our knowledge of the structure and affinities = 
of the plants of the coal-measutes. Entering the field of paleontological ie 
science in 1833 asa contributor to the “Fossil Flora of Great Britain” 
by Lindley & Hutton, almost every year since has witnessed the produc- ey 
tion from his pen of papers of more or less extent, describing in detail = 
the histology and relationships of carboniferous plants. The last is the ee 
elaborate and beautiful memoir before us. . Et 
Stigmaria ficoides is one of the most abundant and well-known plants a 
of the carboniferous age. It is most frequently met with, however, in ae 
the form of inorganic casts of the starred exterior or of the fistular medul- ik 
lary interior. As these casts were the only conditions under which it 
was kaown fora long tim3, th? histology, and consequently the affinities, 
long remained in question. During the last half-century, however, spec- 
imens have been obtained from various localities in which the structure 
has been more or less clearly preserved, and through a study of these _ 
considerable light pas been thrown upon the affinities of these curious © 
plants. 
, S8€ams, 
The results of a study of the histological elements in these speci- 
mens, briefly stated, are as follows: The medulla was composed exclu- 
sively of parenchymatous tissue, and early, by absorption or decay, became 
hollow. Into this fistular medullary cavity stigmarian or other rootlets 
penetrated, sometimes to the number of half a dozen, thus causing great 
complication. These specimens, to the casual observer, would appear too? 
_ be traversed by fibro-vascular bundles, and by a study of such specimens 
Several observers were led into error ; es 
urrounding the medulla was a vascular or xylem cylinder composed 
of transversely barred vessels or tracheids, These tracheids, arranged in” 
bundles, did not preserve a longitudinally straight, but an undulating 
Course through the stem, the undulating curves of one bundle being op- 
Posed to those of its neighbor on either side. “ The result of the wavy 
undulations was that contiguous bundles alternately touched and sepa S 
Fated from one another, inclosing, in the latter case, large, vertically os 
elongated lenticular spaces, occupied by extensions of the medullary par- — 
enchyma which thus reached the bark. Asthe vascular cylinder grew 
Stigmaria’ ficoties (The Paleontographical Society, volume for 1886.) 
Plates. London, 1887. 
