296 



Dr. P. F. Frankland and Mrs. Frankland. [Mar. 13, 



an addition to our knowledge of the great Calamarian family, to 

 which, the plant obviously belongs. 



Further demonstrations are also given by the author, illustrating 

 some features in the history of the true Calamites. Attention is 

 called to the fact that, whilst the large, longitudinally-grooved and 

 furrowed inorganic casts of the central medullary cavities of these 

 plants are extremely common, we never find similar casts of the 

 smaller branches. The cause of this is demonstrated in the memoir. 

 In these young twigs the centre of the branch is at first occupied by 

 a parenchymatous medulla. The centre of this medulla becomes 

 absorbed at a very early age, leaving the beginnings of a small 

 list alar cavity in its place ; but, if any plastic mud or sand entered 

 this cavity when the plant was submerged, the surface of such a cast 

 would exhibit no longitudinal groovings, because there would be 

 nothing in the remaining medullary cells surrounding the cast to 

 produce such an effect. It was only when the further growth of the 

 branch was accompanied by a more complete absorption of the 

 remaining medullary cells, causing the cavity thus produced to be 

 bounded by the inner wedge-shaped angles of the longitudinal 

 vascular bundles constituting the xylem zone, that such an effect 

 could be produced. After that change any inorganic substance 

 finding its way into the interior of this cavity, had its surface so 

 moulded by the wedges as to produce the superficial longitudinal 

 ridges and farrows so characteristic of these inorganic casts. 



II. " The Nitrifying Process and its Specific Ferment." By 

 Percy F. Frankland, Ph.D., B.Sc. (Lond.), A.R.S.M., &c, 

 Professor of Chemistry in University College, Dundee, and 

 Grace C. Frankland. Communicated by Professor 

 Thorpe, F.R.S. Received February 28, 1890, 



(Abstract.) 



The process of nitrification has been practically studied for cen- 

 turies, but it was first in the year 1878 that it was shown by 

 Schloesing and Miintz to be dependent upon the presence of certaiu 

 minute forms of life, or micro-organisms, or in other words to be a 

 fermentation change. 



The authors have been engaged during the last three years in en- 

 deavouring to isolate the nitrifying organism, and the present memoir 

 gives in detail an account of the numerous experiments which were 

 made in this direction. 



Nitrification, having been in the firpt instance induced in a par- 

 ticular ammoiiiacal solution by means of a small quantity of garden 



