402 Dr. G. Ogilvie on the Forms and Structure of Fern-stems. 



These varieties depend on the relations and proportionate 

 development of the principal structural elements — the proper 

 axis, the rootlets, and the fronds, whose bases remain perma- 

 nently attached to the stem after the leaf-like portions have 

 withered and decayed away. Organs corresponding to these 

 enter into the constitution of all the higher plants. In the 

 larger forms of vegetation, they are clearly marked off from each 

 other by a wide local separation, the radical fibres coming off 

 from one extremity of the stem, and the leaves from the other ; 

 but this arrangement is not an essential of the vegetable orga- 

 nization ; for in various subterranean and creeping stems, such 

 as those of the rose and the iris, the strawberry and many 

 grasses, we have both rootlets and leafy shoots coming off side 

 by side from a greater or less extent of the vegetative axis ; and 

 even where this assumes an arborescent character, such inter- 

 mixture, though less frequent and less complete, is still an 

 arrangement of occasional occurrence, as in the Banyan and 

 other species of Ficus, Pandanus, Dracaena, &c. All these va- 

 riations we have represented in Ferns. In Tree-ferns, as in 

 arborescent forms of other types of vegetation, we have the 

 length of the stem interposed between the rootlets and the bases 

 of the fronds; and though generally, when the plant attains 

 some height, adventitious roots are emitted from the sides of the 

 stem, still they spring from its lower part, and are separated 

 from the growing leaves by a very considerable interval. But 

 in our indigenous species the stems are all more or less of the 

 kind termed rhizomes by botanists, and emit rootlets and leaf- 

 stalks side by side along their whole extent, or nearly so ; and, 

 as has just been remarked, it is to diversities in their disposition 

 and proportionate development that the variations in the form 

 of the stem are in great measure due. 



In the first or stoloniferous variety, the axis is long, slender, 

 and much branched, its subdivisions running horizontally along 

 or just under the surface of the ground, and sending off from 

 below numerous black wiry rootlets, and from the upper aspect 

 the scattered petioles of the fronds. The extremities of the 

 rhizome are scaly, the petioles smooth and naked. When a root 

 of this kind is dissected out of the soil — an operation involving 

 no small expenditure of time and trouble, from its tortuous and 

 brittle character — we can readily distinguish the formations of 

 successive years. At the growing points of the stolons we have 

 the petioles quite fresh, and still bearing leaves ; behind these, 

 we have the bases of the last and former years' fronds in different 

 stages of decay ; and lastly, only the creeping stem itself, and 

 this, as we trace it backwards, in a continually increasing state 

 of decay, which finally makes it impossible to follow it any fur- 



