254- Rev. P. Keith on the External Structure 



tion. Yet in Equiselum the trunk is a jointed and upright 

 stem ; in Pilularia it is jointed and trailing; in Li/copodium it 

 is lash-shaped and creeping. Ferns strictly so called have no 

 branches ; yet in the Lycopodiacecc and Equisctacece branches 

 are to be found. In the latter they issue in whorls; in the 

 former they do not originate in any regular order. Among 

 ferns, leaves are not to be met with, at least as distinct and 

 separate organs, except in Lycopodiacece and Marsiliacecc, 

 which tribes, together with the Equisetacece, have so much that 

 is peculiar to themselves respectively, that botanists now ar- 

 range them as distinct orders*. 



It was for a long time thought that ferns were destitute of 

 seeds and propagated nobody knows how; yet there is no 

 botanist of the present day who doubts the reality of fern 

 seed, or at the least of sporides from which new plants spring. 

 Some botanists have even fancied that they had detected the 

 parts of the antecedent flower f. But admitting that such de- 

 tection is impracticable, the botanist can, at least, direct his 

 attention to the mode of fructification, and to the fruit or 

 sporide produced. In ferns strictly so called the fructifica- 

 tion is dorsal, that is, scattered in patches or clusters— son — 

 on the back of the frond. These patches are generally ac- 

 companied with an integument called the indusium, which at 

 the period of the maturity of the seed bursts open, sometimes 

 towards the nerves, and sometimes towards the margin, but 

 in plants of a similar habit uniformly in a similar manner. 

 Hence its utility in determining natural genera, first disco- 

 vered by Sir J. E. Smith \- When the indusium bursts, the 

 fruit, now ripe, escapes, which is, for the most part, a capsule 

 surrounded by an elastic and jointed ring, opening trans- 

 versely, and discharging the inclosed seed or sporule, which 

 is a small and minute globule, discoverable only by the aid ot 

 the microscope. In Lycopodium the fructification is axillary, 

 in Equisetum it is terminal, and in Isoetes and Pilularia it may 

 be said to be radical. 



TheMusci,or Mosses.— The mosses are a tribe of imperfect 

 plants of a small and diminutive size, consisting often merely 

 of a root, surmounted with a tuft of minute leaves, from the 

 centre of which the fructification springs, but furnished, for 

 the most part, with a stem and branches, on which the leaves 

 are closely imbricated. Their most favourite habitats are 

 bleak and barren soils, such as mountains, heaths, woods, 

 where they are not only rooted in the earth, but attached also 



• Hooker's I3ritit.li Flora, p. 438. I llcdvvig, Theor. Fried, it (ic/wr. 



I Smith's Tracts, 287. 



