TRANSFORMATIONS OF THE LEAF. 66 



309. Nepenthes. The greenhouse pitoher-plant ia a native of the Bast Indies. 

 Its proper leaves are sessile and lanceolate. The midvein extends beyond the apex 

 like a tendril, to the length of six or eight inches. The extremity of this tendril is 

 inflated into a hollow vessel, similar to a pitcher, and usually contains about half a 

 pint of pure water. It is furnished with a leafy lid connected to it by a ligament 

 which expands or contracts according to the state of the atmosphere, so that the 

 cap is open In damp weather and closed in dry. 



310. DlsoiiiDiA. Another wonderful provision of this kind is observed in a plant 

 growing in the forests of India; called Disohidia. It is a twining plant, ascending 

 the tall trees to the distance of a hundred feel from its roots, and destitute of leaves 

 except near its top. The pitchers seem formed of a leaf with its edges rolled in- 

 ward and adherent, and its upper end or mouth is open to receive whatever moist- 

 ure may descend into it. But the greatest marvel in its structure is that several 

 bundles of absorbent fibres, resembling roots, are sent out from the nearest parts of 

 the stem, enter the pitchers,, and spread themselves through the cavity. 



311. Air bladders. Many weak-stemmed water plants are furnislied 

 with little sacks filled with air to buoy them up near to the surface. 

 Such are the bladders of the common bladderwort, formed from the 

 leaf lobes. In the horned-bladderwort the floats are made of the six 

 upper inflated petioles lying upon the surface of the water like a wheel- 

 shaped raft, and sustaining the flower upon its own elevated stalk. 



312. The leap op Venus' flt-teap (Diouea), native of Carolinaj is also of curious 

 design. At the end of the leaf are two 

 lobes bordered with spines. In the •^i^^^^^i4/ 

 cavity between the lobes are several 

 sharp points projecting upwards, and a 

 gland which secretes a liquor attractive 

 to insects. But when an unlucky fly, 

 in search of food, alights upon it, the 

 irritable lobes instantly close and im- 

 pale him in their fatal embrace. 



313. The Tendril is a thread- 

 like coiling appendage furnished* 

 to certain weak-stemmed plants as 



their means of support in place. 17s, Leaves of Venus' fly-trap (Dionea). 



Its first growth is straight, and it remains so until it reaches some oh- 

 ject, when it immediately coils itself about it, and thus aquires a firm, 

 , though elastic hold. This beautiful appendage is finely exemplified' in 

 the Cucurbitacese and grape, above cited ; also in many species of the 

 pea tribe (Leguminosse), when it is appended to the leaves. It is not 

 a new organ, but some old one transformed and adapted to a new pur- 

 pose. In Gloriosa superba the midvein of the leaf is prolonged beyond 

 the blade into a coiling tendril. In the pea, vetch, etc., the tendrils 

 represent the attenuated leaf blades themselves. Again, the entire leaf 

 sometimes becomes a tendril in Lathyrus, while the stipules act as 

 leaves. 



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