SPECIAL MORPHOLOGY : THE HORSETAILS. 



199 



centre. From five to seven hemispherical sporocarps are developed 

 from and upon the lower and inner surface of the disc. Two 

 layers of the cellular tissue of these form the wall of the fruit. 

 The inner cells become parent cells (sporangia), and from each of 

 these one spore is produced from a distinct cytoblast. Two spiral 

 fibres are simultaneously formed in the parent cell, which at first 

 completely cover the inner wall, are rounded off at both extremities, 

 and somewhat flattened out, and are firmly closed together. The 

 spiral coils are subsequently somewhat separated by the expansion 

 of the parent cell. When the spores are quite mature, the hvgro- 

 scopical spiral bands tear the delicate wall of the parent cell, and 

 wholly separate from each other, although they remain adhering by 

 the centre to the spore. The sporocarps then split longitudinally, 

 and emit the spores. 



The whole fructification of the Equisetacece (fig. 147. A, B) is not to 

 be distinguished setting aside the actual development of the parent 

 cells of spores (fig. 148. A D) from the antheriferous inflorescence of 



14' 



148 



Tax-us* by any morphological or anatomical characteristic, on which 

 even a merely specific distinction can be established. This peculiarity 

 was, however, for a long time put under contribution by the fancy of 

 botanists, and, as may naturally be supposed, the antheridia mania did 

 not suffer the Equisetacece to escape. As nothing else appeared, the 

 unfortunate spiral fibres were chosen, as occasionally a few mucus 

 granules might be seen adhering to them. As early as 1833f Mohl gave 

 a correct explanation of these, and I myself had often followed the history 

 of their development, which it is extremely easy to do, always arriving 



* Compare also Mohl's Sporang der Kryptog. p. 7. 



f Mohl, Flora of 1 833, on the Spores of Cryptogamic Plants, p. 1 5. ; and the work 

 before quoted. 



147 Equisetum limosum. A, Fruit-bearing extremity of the stem, 

 leaf, seen from the side ; magnified strongly. 

 118 Equisetum arvense. 



B, Separate spore- 



A, Young mother-cell, with a spiral layer of thickening : the 



dotted lines show the spore shining through, with its large cytoblast. B, The same 

 mother-cell, seen from above. C, The spore from it. D, Completely developed 

 mother-cell, with the spore in it ; a, interval between the turns of the spiral fibres. 



o 4 



