1912] CURRENT LITERATURE 259 
siphonostelic ferns in which the medullary rays are narrow or lacking. These 
feature forms are interpreted as an evolutionary series in which the outstanding 
is the development of a stelar pith by means of a reduction of the central 
tracheids and their replacement finally by parenchyma. It would be difficult 
to prove or disprove this view. That a stelar pith might originate in this way 
or by an expansion of the stele, as in the roots of many of the higher plants, 
is unquestioned. But that these fossils represented evolutionary stages which 
culminated in the conversion of a part of a stelar pith into phloem and endo- 
dermis, as in Osmundites skidegatensis or Osmunda cinnamomea, is unsupported 
by evidence of any kind 
WYNNE-VAUGHAN and Bower accept JEFFREY’s hypothesis as to the 
gene character of the pith in every other family of ferns, but in dealing 
the Osmundaceae they cloud the issue by apparently confusing two 
problems. From a limited series of imperfect fossils they have tried to dis- 
cover when and how cortical tissues might have been enclosed by the stele. 
Failing in this, they conclude that they probably could not have been included 
at all. But neither are we sure when and how that happened in the other 
families, and a search through the known fossil representatives would prob- 
ably end as unsatisfactorily as in the case of the Osmundaceae. Research so 
far has been successful mainly in verifying the theory that the filicinean pith 
_ is extrastelar, and with such forms as Onoclea, in which the pith consists 
partly of epidermal tissues and the atmosphere, there is scarcely any escape 
from accepting it, just as these botanists have done. It is true that the 
evidence in Osmunda is not as striking as in Onoclea, but it is quite as striking 
as in many other forms with extrastelar piths. There are representatives of 
the Osmundaceae in which the central pith, peripheral pith, internal endo- 
dermis, and internal phloem are texturally like those of the outer cortex, inner 
abundant instances of what in other groups would readily be conceded vestiges 
of portions of amphiphloic siphonosteles. Applying the same standards of 
interpretation of anatomical phenomena to all the Filicales, it seems reasonable 
to maintain that the kind of evidence that has carried conviction in every 
case but one must hold in all. The question as to when and how the extra- 
stelar pith originated is quite another matter, and I venture to affirm that 
observations on such features as the relative position of a tracheid and a paren- 
chyma cell in the xylem of a sporeling, or the shape of medullary rays in an 
‘adult, will help little in its solution —J. H. Fautt. 
Biology of lichens.—In his culture studies ToBLeR™ used Cladonia 
glauca Floerke and C. squamosa (Scop.) Hoffm. By carefully scraping the 
branches, clusters of soredia were separated. These were sown on sterile 
* TosLer, F., Zur Biologie von Flechten und Flechtenpilzen. II. Die Entwick- 
lung der Cladonia-Soredien. Jahrb. Wiss. Bot. 49:409-417. pl. 3. figs. II. 1911. 
