VASCULAR CRYPTOGAMS 



The sporanges of the Equisetaceas are collected into teraiinal spicate 

 ' fructifications ' of a cone-like or catkin-like character, resembling 

 nothing else among existing Vascular Cryptogams. These are borne at 

 the extremity either of the ordinary green vegetative stems, whether 

 branched (E. palustre, L.) or unbranched (E. hyemale, L.), or of special 

 fertile stems (E. arvense, pratense, Ehrh., maximum. Lam.), which are 



then always simple, even when the 

 barren stems are branched, and are 

 usually stouter, nearly or quite desti- 

 tute of chlorophyll, and with much 

 larger leaf-sheaths and coarser teeth. 

 As already mentioned, these can be 

 artificially converted into vegetative 

 stems ; and occasionally deciduous 

 fructifications are borne at the extre- 

 mity of the ordinary green branched 

 stems, in species which normally pro- 

 duce special fertile stems (E. arvense). 

 The sporanges are not, like those of 

 typical Fihces, trichomic or epidermal 

 in their origin ; their development 

 closely resembles that in the Marat- 

 tiaceee. They are endogenous out- 

 growths of peculiarly metamorphosed 

 leaves, \\\t. peltate scales or sporophylls, 

 arranged, like the branches, in whorls. 

 Intermediate between these and the 

 uppermost whorl of ordinary leaf- 

 sheaths there is (in E. maximum) a 

 whorl of barren but more or less 

 modified leaf-sheaths, forming a small 

 annular girdle, the involucre or an- 

 nulus. The whorls of sporangiferous 

 scales, of which a number are formed 

 above this involucre, make their first 

 appearance as similar annular girdles, 

 projecting but slightly from the stem, but gradually forming a hemi- 

 spherical cushion. This cushion finally breaks up into a number of 

 plates, the surface of which is parallel to that of the stem ; and these, by 

 mutual pressure, become polygonal and usually hexagonal ; each plate 

 or disc is attached to the stem by a slender pedicel at right angles both 

 to its surface and to that of the stem. On the inner surface of these 



Fig. 83. — A, upper part of fertile stem of £. 

 itiaxintuin (natural si2e); b, leaf-sheath; 

 a, annuius ; jr, sporophylls and their 

 stalks. Bj sporophylls ( >: 6) ; sg, spo- 

 ranges. (After Goebel.) 



