Development in Equisetum . 67 
to a place among the Gymnosperms ; and emphasized this 
change by altering the name Calamitea to Calamodendron. 
He thus asserted the existence of two genera, one to be 
placed side by side with modern Equisetaceae, the other to 
be included among the Gymnosperms. 
Goppert gave generic value to Cotta’s two species calling 
them Calamodendron striatum and Arthropitys bistriata. 
Grand ’Eury accepted the change, thus arriving at the 
classification shown in the last column of the foregoing table 
which represents the view held by what has been termed the 
French school, headed by Brongniart, Grand ’Eury and 
Renault, together with Schenk. 
The group Calamodendrees (Calamodendreae) was thus 
understood to consist of Calamitae which show secondary 
thickening ; together with the casts and impressions referable 
to such forms. 
The name Catamites (Calamiteae) was reserved for such 
Calamitae as may be shown to have no secondary thick- 
ening ; together with casts and impressions referable to such 
forms. 
There is however no evidence to show that Calamitae 
devoid of secondary thickening ever existed All specimens 
which show minute structure exhibit such thickening. Schenk 
proved that in certain remains from which secondary thick- 
ening was held to be absent, the supposed cortex was really 
secondary wood. 
Grand ’Eury himself has recently admitted that in the 
cases of Catamites cannaeformis and Catamites varians (forms 
considered by the French school as referable to the class 
devoid of secondary thickening), we have casts derived from a 
type which shows secondary thickening, namel y, Arthropitys 1 . 
Under the circumstances we may now limit our attention 
to consideration of such forms as possess secondary thick- 
ening, that is, to all Calamitae of whose minute structure we 
have any record. 
Williamson’s paper, in the Memoirs of the Manchester 
1 Comptes Rendus, 1886, p. 394. 
