Horsetails 



which hang from each scale, rupture, and the spores are 

 liberated. 



The stems, which are marked by longitudinal ridges 

 and hollows, abound in flinty particles. Owing to the 

 presence of these flinty particles, horsetails were once 

 much utilised in the polishing of marble, metal goods, 

 woodwork, etc., especially one species, popularly called 

 Dutch Rushes, which is still exported from Holland for 

 that purpose. 



In addition to the upright stems there is a much 

 branched underground stem, or rootstock, which by 

 choking up drainage cuttings and ditches often proves 

 exceedingly troublesome to farmers and others. 



Horsetails are allied to ferns in that they, like ferns, 

 are reproduced indirectly from spores with the inter- 

 vention of a prothallium stage. The prothallia, 

 however, are of two kinds, male and female, the former 

 bearing the male organs only, and the latter, the female, 

 Both kinds of prothallia are produced from similar 

 spores, and the question as to whether a spore will 

 become a male or a female prothallium seems to depend 

 on the nutriment present when the spores germinate. 

 These spores which are very minute and of a light- 

 green colour have a very interesting property. If they 

 be shaken from the cone on to a sheet of white paper, 

 they instantly jump about, as if alive, but, if a few 

 drops of water from a pin-point be dropped upon them, 

 they become quiescent at once. Their power of move- 

 ment may be even better noted, if a few of the moist 

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