42 Our Native Perns. 



78. Stipe. — The stipe is made 

 up of the three forms of tissue, 

 (Fig. 28), and usually contains sev- 

 eral bundles of vascular tissue. In 

 the dried stipe these can be easily 

 examined, by scraping off the ex- 

 ternal covering of the stem . These 

 bundles of fibres givff stability to 



the fern and are continued through „. „„ „ „ , ^. 



. . Fig. 28. Cross section of stipe of Cys- 



the rachisesand vems thus formmg ^^^j^ j^gg^is, Bemh., showing two 



the framework for the softer por- bundles of vascular tissue. (Original.) 



tions of the frond. The stipes are sometimes smooth and polished, 

 sometimes hairy or beset with stalked glands, and sometimes 

 densely clothed, especially near the base, with chaffy scales. 



79. Frond. — In the HYMENOPHVLLACEiE, the frond consists 

 of a single layer of cells. This condition is also found in the leaves 

 developed along the axis of growth among the mosses to which 

 this sub-order is related in some of its forms. In all other ferns 

 there are several layers of cells variously compacted together and 

 forming all the varieties of texture, membranous, herbaceous, 

 coriaceous and fleshy. The epidermis is usually easily separable 

 from the underlying tissue, when its peculiar markings can be 

 studied. 



From the epidermis a great variety of appendages are de- 

 veloped which are all modifications of hairs and are all included 

 under the term trichomes, however different in appearance or dis- 

 tinct in function. These are not confined to the frond but develop 

 here their greatest variation. They are frequently found on the 

 roots, the rhizoma, and the stipe, under the form of root-hairs or 

 scales of various forms. Scales are especially abundant in certain 

 forms oiAspidium, as well as in Scolopendrium and other genera. 



80. Trichomes. — On the fronds the trichomes may be devel- 

 oped as simple unarticulated or articulated hairs, consisting of 

 one or two cells at most. They may appear as stalked glands like 

 those that arise from the stipe of Cheilanthes Cooperce or the mar- 

 gin of the indusium of Aspidiutn spitmlosutn, var. intermedium ; 

 or they may be developed into scales of intricate cellular struc- 

 ture like those on the under surface of certain forms of Cheilanthes ^ 

 particularly C. Fendleri axiA-C. Clevelandii. Among the Filices 

 the sporangia are specialized trichomes developed in clusters 

 (sort) along the veins, or spread over the entire surface of the 

 frond, or even arranged in spikes or panicles. The epidermis also 



