126 



VASCULAR CRYPTOGAMS 



which must be referred to the same group. To the same family as 

 Calamites belong probably Astromyelon (Will.), and at least some 

 species of Arthropitys (Gopp.). The degree of identity in structure of 

 Calamodendron with Calamites is a point on which the best authorities 

 are not yet in agreement. 



To the genus Calamitina (Weiss) (Asterophyllites, Ren., Calamocladus, 

 Schmp.) belong a number of calamite stems found with the leaves still 

 in connection with them. These are of very peculiar form, consisting 

 of an ovate-lanceolate basal portion, thickened and marked by a central 

 furrow, and a narrowly-lanceolate acuminate apical portion ; the basal 



Fig. 97.— Stems of Calamites. (After Weiss.) 



portion alone being very frequently preserved. The leaves do not 

 coalesce laterally into sheaths ; on falling off they leave behind whorls 

 of round or ovate scars. Bornia (Brongn.) (Archeeocalamites, Stur) is 

 an older fossil occurring in the Devonian formation, differing from the 

 more recent forms in the broad flat longitudinal ribs on the stem not 

 alternating in adjacent internodes. 



In Annularia (Brongn.), which occurs only in the Carboniferous 

 formation, the leaves are linear- lanceolate, and are penetrated by a single 

 ' vascular ' bundle ; those of each whorl are united laterally in their 

 basal portion into a shallow saucer-shaped cup, through which the stem' 



