HICK : SOME RECENT ADVANCES IN BRITISH PAL.EOBOTAN Y. 45 
was intimated that additional information was being accumulated.* 
Since then, the late Prof. Williamson and Dr. D. H. Scott have 
re -investigated the matter, and have published their observations in a 
joint memoir contributed to the Philosophical Transactions for 1893. 
These observations deal with numerous questions of anatomy and 
development, which previous researches had left unanswered, and 
bring our knowledge of these stems much nearer the level of that of 
recent plants than had been possible before. In the main, however, 
they refer to the stem of Calamites after the secondary changes it 
usually exhibits had made some advance, and the primary condition 
is not so fully dealt with. 
Last year I was able, in some measure, to make up for this by 
publishing a series of fresh observations specially bearing upon the 
primary structure of the Calamitean stem,! as found in a type of 
Calamites which is very common in the Lower Coal Measures of 
Yorkshire. Without going into details, for which the paper itself 
must be consulted, it may be submitted that those who will read it 
along with the much more elaborate memoir by Williamson and Scott, 
will admit, that from a very early to a somewhat late stage of 
development, the stem of Calamites is quite as well known as those 
of the majority of recent plants. It is not certain that all the stems 
dealt with by Williamson and Scott are of the same species as those 
described in my paper, but in spite of this, the one set may be 
regarded as complementary to the other, until we are able to 
distinguish individual from specific differences. All the same it may 
be worth mentioning that my specimens are of the type known as 
Arthropitys, which seems to be the one that is most abundant in the 
Lower Coal Measures of Yorkshire. A notable feature in them is 
the peculiar character of the inner cortex, which consists of relatively 
large cells, but of difi'erent sizes, containing masses of black car- 
bonaceous matter. These cells form a continuous zone of tissue 
which I have elsewhere named " melasmatic " tissue. 
The Leaves. — As in the case of the roots, so in that of the 
leaves of Calamites, it was necessary to admit in 1891 that little or 
* Loc. cit., page 4. 
t Mem. and Proc. of the Manch. Lit. and Phil. Soc., series 4, vol. viii., 189.3-4. 
