368 



FR UCTIFICA TION. 



PART II. 



From the rhizome, which often extends to a great 

 length, the stems of the Equisetums rise in the form 



of rough, rigid, hollow 

 cylinders, striated lon- 

 gitudinally, and articu- 

 lated at intervals by se- 

 parable joints. Each 

 articulation is invested 

 at its base by a toothed 

 membranaceous sheath, 

 from beneath which, in 

 the greater number of 

 the species, whorls of 



Fig. 70. Eqnisetum gigantettm : a, fragment of branches SPrinfiT. lointed 

 stem with branches ; b, cone or spike of f rue- , . . 



tification ; c, one of the scales of the cone ; d, like the stem, and Simi- 



spore with its elastic filaments. , 



lar to it even to the 



number of teeth in the sheaths and strise on the sur- 

 face, but unbranched. 



The fructification is occasionally on separate stems, 

 which make their appearance before the barren ones, 

 and are in general unbranched and succulent, bearing 

 a cone on their apex. The surface of the cone is at 

 first smooth or indistinctly reticulated, but it eventually 

 splits into numerous octagonal, brown, shield-like discs, 

 spirally arranged, which, separated from the stem, are 

 found to have a stalk, and to bear on the under-side 

 four or eight pendent sac-like bodies of a whitish hue. 

 These are the sporangia, which open on the inside by a 

 slit for the discharge of the spores. The inner coat of 

 the cells of the sporangium is composed of beautifully 

 spiral tissue. The spores arise by cell division, each 

 being covered by a separate membrane, which ultimately 

 forms a pair of elastic fibres attached by their middle, 

 closely coiled round the spore, as it is formed within 

 the cell ; but, when the spore is liberated, they extend ; 

 the least moisture, however, even the breath, makes 

 them contract. 



