4 THE FERNS AND 



divisions or lobes, but as the cutting does not extend to tlie midrib, 

 the blade is still all of one piece and therefore simple. It is, how- 

 ever, said to be pinnately lobed, and the correct term to apply to it is 

 pinnatipartite. Had the incisions extended only about half-way from, 

 the extremity of the lobes to the midrib, the leaf would have been 

 termed pinnatifid. In describing the shape of such a frond, an 

 imaginary line is drawn round the tips of the lobes, so that the- 

 general shape of the outline is given ; in this case it might be 

 described as broadly elliptical-ovate. The frond A 3 is linear, as are- 

 the lobes of A 4, while the apices of both fronds are acuminate. At 

 the left side of the rhizome a small entire frond is figured, which i& 

 linear-oblong in shape with a sub-acute apex, while the very small 

 frond on the extreme right is also linear-oblong, but with an obtuse 

 apex. 



On the back of the mature fronds, and placed on the secondary 

 veins, are two rows of orange-brown spots, varying from yV^'i *° 'h^^^ 

 of an inch in diameter, commonly known as the seed, but called by 

 botanists the sori (sing, sorus). These sori are groups or collections 

 of the reproductive organs, and their presence on the back of a frond 

 is one of the chief points of difference between fronds and ordinary 

 foliage leaves, as the latter do not — in flowering plants at least — - 

 bear these organs. If a single sorus is examined — and here the aid' 

 of a good magnifying lens will be needed — it is found to consist of a 

 number of minvite oval bodies (the capsules or sporangia, see PI. I. 

 fig. 4a) joined by a short stalk to the frond. These capsules are- 

 nearly surrounded by a jointed ring or band (the annulus), which 

 passes vertically over them, and which, by its elasticity, serves to- 

 rupture them when mature. The bursting of each capsule liberates- 

 a number of minute rounded or triangidar bodies — the spores — which 

 fly out as a fine dust. This dust is frequently spoken of as fern-seed, 

 but the term is quite incorrect, as a spore is not a seed, but is more- 

 comparable to a miscroscopic bud. 



If we now take Lomaria Jhiviatilis (fig. B), we shall find the same 

 parts, but -with very considerable diversity of form. Here the 

 rhizome (fig. B 2) is short and erect, being rendered thick by the bases 

 of old stipes which remain attached all round it, while the fronds 

 stand in a tuft from its upper end. Such a rhizome is often called 

 a. rootstock ; and though so different in length and appearance from- 



