448 CASH : FOSSIL FRUCTIFICATIONS OF YORKSHIRE COAL MEASURES. 
Sporangia 
Equisetum. Calamostachts. 
/aiTanged around the /arranged around the 
Spores - 
( Mic=microspores, 
mac = macrospores 
j inner surface of the 
peltate discs so that 
they he nearly at 
right angles to the 
central axis of the 
\fruit-spike 
nume r o u s , small, /numerous small spores 
nearly 
inner surface of the 
peltate discs so that 
they lie nearly at right 
angles to the central 
axis of the fruit-spike. 
uniform m 
size (microspores) and 
(microspores) having 
no elaters, and in C. 
provided with elaters^ Casheana, Y^illiamson, 
there are also present 
large spores , macro- 
spores. 
There have appeared in Nature" two communications respect- 
ing the spores of Equisetam^ which, if they may be relied upon, will 
certainly tend to bring Eqnisetum and ^ 'alanwdtachys into a nearer rela- 
tionship than they are now regarded as occupying by most palce- 
botanists. One of these states that a living species of Equisetum pro- 
duces macrospores, the other one says that '''The remarkable Equisetum 
littorale, differing from all other species in the absence of elaters, is 
recorded as British (and figured) by Mr. Beeby, on the faith of 
specimens from Surrey. Journal of Botany, March and April, 1887. 
Nature, 19th May, 1887, p. 70. I have seen neither of these species, 
and cannot help thinking that there is some error in observation, at 
any rate, until these supposed discoveries are confirmed, one must 
not use them in any way to modify ones views of the relationship of 
Calamostacliys to Equisetum. 
Sir J. "VV. Dawson evidently regards Calamostacliys as the fruit of 
some species of Calamites, or at least of some allied Equisetaceous 
plant. In his work on " The Geological History of Plants," lately 
published (in the International Scientific Series, Vol. LXIIL, Lond., 
1888, p. 123-5), he thus speaks on this question: '"'All Calamites 
were not alike in structure. In a recent paper, Dr. Williamson 
describes three distinct structural types. ]\Iemoirs of the Philo- 
