84 BOTANICAL GAZETTE [JULY 
climates; but that only the method of accumulation by drift takes place in the 
tropical climates, nothing corresponding to a peat bog of the temperate climates 
having been found in the tropics. As the result of microscopic examination of 
coal he concludes that the allocthonous hypothesis also harmonizes best with 
the structure of coal. This is in harmony with the view of some that the 
climate of the coal-forming epochs approached present tropical conditions. 
The canneloid coals, such as the true cannel coals, tasmanite, and boghead 
coals, are composed chiefly of spores, now very much crinkled and collapsed, 
owing to improved methods can now be identified as spores. These coals have 
been formed under open water, representing the muck of ancient lakes or 
lagoons. 
The ordinary bituminous coals are composed of both woody or lignitoid 
material and spore or canneloid matter in varying proportions. The wood 
or lignitoid constituent; known in descriptive terminology as glanz coal, is 
found in layers and has lost completely its original organization, a condition 
generally observed in coals derived from vegetable débris. Carbonized wood 
or charcoal is the only material derived from the grosser parts of plant bodies 
which retain structure in coal. Between the shiny woody or lignitoid layers 
are lodged the duller canneloid layers, known in descriptive terminology as 
matt coal, consisting of a dark ground substance in which are imbedded remains 
of flattened spores. 
Coals, therefore, may be composed of three recognizable constituents: 
(1) spores or canneloid, (2) modified wood or lignitoid, and (3) less commonly 
relatively unmodified carbonized wood or charcoal. The properties of coal, 
he conjectures, depend to a very large degree upon the proportions of the 
original constituents; coals rich in spores, such as cannels, bogheads, and oil 
shales, are highly bituminous, and in some form or other are the mother sub- 
stance of oil and gas. The spore contents of a coal determine the fatness, and 
in all probability have a definite relation to its coking properties; the lignitoid 
constituent, on the other hand, reduces the bituminosity and coking value of 
coal.—REINHARDT THIESSEN. 
If-sterility in Nicotiana.—East™ has studied self-sterility in hybrids 
fertile plants occur in at least one of the parent species. All the hybrids tested 
(over 500 plants of F,, F., F;, and F,) were self-sterile. The F, plants, like the 
parent species, had go-100 per cent of morphologically perfect pollen, except 
for a single plant oi only 2 per cent of good pollen. Cross-pollination 
between individual plants of F,, F;, and F, demonstrated a high degree of cross- 
fertility. There was found 1.5 per cent of apparent cross-sterility in F., 6 per 
*4 East, E. M., The phenomenon of self-sterility. Amer. Nat. 49:77-87. 1915. 
