CHAPTER XVI 



PHYLUM X. CALAMOPHYTA 

 THE GALA MITES 



463. As far as we know them the Calamites are green 

 plants in which the marked difference between the small 

 gametophytes and the large sporophytes seen in the 

 Ferns is continued, but here the sporophyte stems are 

 mostly hollow and jointed, and the leaves relatively 

 small. A great difficulty in studying the plants of this 

 phylum is that although common in the Paleozoic 

 period, but few (about 24 species) have survived to the 

 present time, and our knowledge of them is confined to 

 what we have been able to make out from fragmentary 

 fossils, helped out in some details by a study of the 

 surviving species. 



464. This much, however, has been made out pretty 

 certainly: Gametophytes small, and short-lived, mostly 

 monoecious; Sporophytes large, long-lived, with roots, 

 and elongated, cylindrical, jointed, often hollow stems, 

 bearing relatively small whorled leaves at the joints; 

 spores alike (isospores), or of two kinds (heterospores), 

 borne in cones of sporophylls (i.e. special spore-bearing 

 leaves). 



465. Like the Ferns the Calamites have well-developed 

 tissues in the sporophyte generation; the vascular 

 bundles are of a higher type (" collateral"), and are 

 arranged in a cylinder in the stem. When these bundles 

 are "open" the stems have the power of increasing in 



261 



