CHAP. III. FERNS. 221 



ginate, either upon the cuticle or from beneath it, in the form 

 of spots, at the junctions, margins, or extremities of the veins. 

 As they increase in growth they assume the appearance of 

 small heaps of granules, called sori ; if examined beneath the 

 microscope these granules, commonly called capsules^ thecce, spo- 

 rangia, or conceptades, are found to be little brittle compressed 

 bags formed of cellular membrane, partially surrounded by a 

 thickened longitudinal ring [gyrus, annulus, gyroma), which at 

 the vertex loses itself in the cellularity of the membrane, and 

 at the base tapers into a little stalk : the thecae burst with 

 elasticity by aid of their ring, and emit minute particles named 

 sporules, from which new plants are produced ; as from 

 seeds, in vegetables of a higher order. Interspersed with these 

 theca; are often intermixed articulated hairs; and, in those 

 genera in which the thecae originate beneath the cuticle, the 

 sori, when mature, continue covered with the superincumbent 

 portion of the cuticle, which is then called the indusium or 

 invohicrum {membranula, Necker ; glandulcB squamosce, Guet- 

 tard). In Trichomanes and Hymenophyllum the thecae are 

 seated within the dilated cup-like extremities of the lobes of 

 the frond, and are attached to the vein which passes through 

 their axis, which is then called their receptacle. In another 

 tribe, called Gleichenece, the thecse have a transverse complete, 

 instead of a vertical incomplete ring, and they are nearly 

 destitute of stalks ; in a third tribe the sori occupy the whole 

 of the under surface of the leaf, which becomes contracted, and 

 wholly alters its appearance : the thecae have no ring, and the 

 cellular tissue of their membrane is not reticulated, but ra- 

 diates regularly from the apex. 



In these plants it has been in vain endeavoured to discover 

 traces of organs of fecundation. Nevertheless, as it was diffi- 

 cult for sexualists to believe that plants of so large a size were 

 destitute of such organs, it has been considered indispensable 

 that they should be found ; and, accordingly, while all seem 

 to agree in considering the thecae as female organs, a variety 

 of other parts have been dignified by the title of male organs : 

 thus, Micheli and Hedwig found the latter in certain stipitate 

 glands of the leaf; Staehelin, Hill, and Schmidel, in the 

 elastic ring ; Koelreuter, in the indusium ; Gleichen, in the 



