70 



STRUCTURAL BOTANY. 



serving to fix such plants firmly upon other plants or trees, 

 while they derive their nourishment wholly from the air. The 

 Long-moss (Tillandsia) and Conopseum are examples. 



J 247, Old Oak trunk with horizontal branch bearing epiphytes and pars- 

 es sites, a, A fern (Polypodium incanum). 6, Epidendrum conopseum). % 

 s Long-moss (Tillandsia). d, Mistletoe (Viscum). e, Lichen. 



209. Parasites Three classes. Very dif- 

 ferent in nature are the roots of those plants 

 247 called parasites, which feed upon the juices of 

 other plants or trees. Such roots penetrate 

 the bark of the nurse-plant to the cambium 

 layer beneath, and appropriate the stolen juices to their own 

 growth ; as the Dodder and Mistletoe. Other parasites, al- 

 though standing in the soil, are fixed upon foreign roots, and 

 thence derive either their entire sustenance, as the Beech-drops 

 and other leafless, colorless plants, or a part of their sustenance,* 

 as the Cow-wheat (Melampyrum) and Gerardia. 



210. Subterranean stems. As there are aerial roots, so there are snbterraneaa 

 Stems. These are frequently mistaken for roots, but may be known by their habitually 

 and regularly producing buds. Of this nature are the tubers of the Irish Potato, the root- 

 stock of the Sweet-flag, the bulb of the Tulip. But even the true root may sometimes 

 develop buds accidentally as it were in consequence of some injury to the upper axis, 

 or some other unnatural condition. 



Review. 197. The root defined. Its office. 108. It? leading propensity. Its proper 

 appendages. Purpose of their multiplication. 199. Where is the collum? Wheie the 

 spongelets? What are they? What are the fibrillje ? Their office and history. Why 

 should a tree be planted in Spring f 200. Name the two modes of root-development'. 

 Define the axial. 201. Define the inaxia'. Give instances. 202. Four varieties of axial 

 or tap roots. Define the ramous. 203. Define the fusiform The conical The napiform. 

 What the nature of these fleshy roots ? 204. Six varieties of inaxial roots. What of the 

 fibrous? Fibro-tuberous? Nodulous? Moniliform? Coralline (240)'? 20r>. What is 

 stored in them? 20(5. What are adventitious roots? The cirrhous? The fulcra? 207. 

 Trunks of the Banian. 208. Epiphytes. 200. How do the parasites differ? Mention 

 three classes. 210. Distinguish roots from stems. 



