cash: fossil fructifications of YORKSHIRE COAL MEASURES. 4491 
sophical Society," Manchester, 1886-87.) What he regards as tj^pical 
Calamites has, ia its woody zone, wedges of barred vessels, with thick 
bands of cellular tissue separating them. A second type, which he 
refers to Calamopitus, has woody bundles composed of reticulated or 
multiporous fibres, with their porous sides parallel to the medullary 
rays, which are better developed than in the previous form. The 
intervening cellular masses are composed of elongated cells. This is 
a decided advance in structure, and is of the t}"pe of those forms 
hpcving the most woody and largest stems, which Brogniart named 
Calamodendron. A third form, to which Dr. Williamson seems to 
prefer to assign this last name, has the tissue of the woody wedges 
barred, as in the first, but the medullary rays are better developed 
tlian in the second. In this third form the intermediate tissue, or 
primary medullary rays, is truly fibrous, and with the secondary 
medullary rays traversing it. My own observations lead me to infer 
that there is a fourth type of Calamitean stem, less endowed with 
woody matter, and having a larger fistulous or cellular cavity than 
any of those described by Dr. Williamson. 
There is every reason to believe that all these various and com- 
plicated stems belonged to higher and nobler t}^es of mare's-tails 
than those of the modern world, and that their fructification was 
equisetaceous, and of the form known as Calamostachys. 
Calamostachys Binxeyana. Schimp. 
This fruit spike consists of verticils of bracts arranged around a 
central axis ; these are fertile bracts and sterile ones which succeed 
each other in alternate order. 
The sterile bracts form a sort of circular, horizontally placed 
foliar disc, which, on nearly reaching the surface of the fruit 
spike, breaks up into verticils of leaves which bend abruptly upwards 
nearly at right angles, and largely overlap the next sterile whorls, 
giving an imbricated arrangement on the exterior of the spike, these 
leaves, usually twelve, are double the number of the fertile bracts 
or sporangiophores. 
The s2)orangiophores are column-shaped organs (usually six), in 
number half as many as the sterile bracts, they are also arranged 
in verticils. 
