114 



The Irish Naturalist, 



[May, 



€i> 



Fig 5. Fig. 6. 



Botrychiuvi Lunaria, Carrowreagh Hill, near Holywood, Co. Down, 



R. LI. P., 1S91. 



The Horsetails are plants with underground creeping stems, 

 which send up at intervals jointed aerial branches, sometimes 

 undivided, sometimes bearing whorls of simple or compound 

 branchlets at each node. The spores are borne on a cone- 

 like head at the summit of the stem. This fruit-structure 

 may be compared to a short stick into which a number of 

 large-headed nails have been driven, so that the heads of all 

 the nails form a cylindrical or egg-shaped surface. The 

 spore-cases are borne on the inner or under side of the heads 

 of these nail-like branches. The leaves are in the Horsetails 

 reduced to a series of dark-coloured minute teeth that surround 

 each node of the stem. The process of assimilation is per- 

 formed by the green stems and their branches. As in the 

 Ferns, we find among the British Horsetails a considerable 

 variation as to which stems bear fructification. In some, 

 such as Equisettim limosiun, or E. hyemale, it is borne by every 

 fully developed stem, or by the majority of them ; but in others, 

 as the common Field Horsetail, E. arvense, and our largest 

 species, E. 77iaxinin7?i, it is borne on vSpecial stems. Two 



