TENDBILS OF YITIS GONGYLODES. 307 



decay or become weak, fall to the ground and grow. Their special 

 purpose would seem, at first, to be the preservation of life through 

 a long season of drought. It would be fair to assume this, be- 

 cause after nearly twelve months' keeping in a dry place, I have 

 found them still plump, full of life, and ready to grow when placed 

 under circumstances of warmth and moisture. They would sur- 

 vive under conditions necessarily fatal to other parts of the plant. 

 Their capacity for retaining life does not necessitate the conclu- 

 sion that this must be their special function ; and I am led to say 

 this, because so far the plant is only recorded from a perpetually wet 

 country. They appear to answer as a means of propagation, just 

 as do the bulbils of a Lily — which fall off and grow, without being 

 able to withstand drought better than the bulbs beneath the soil. 

 Axillary and other bodies that fall off and grow are not un- 

 common. Tiny tubers are produced in the leaf-axils of some 

 species of Begonia ; and curious round tubers are formed by some 

 species of Dioscorea ; bulbils are frequent among bulbous plants ; 



and asexual means of propagation, known by the same term, 

 obtain in Cham, thallus of Hepatieae, and frond of many ferns, 

 &c. ; while the leaves of many species have little plantlets ready 

 to grow on falling to the ground, or which soon develop when 

 the leaves are in contact with moist soil. All these cases differ 

 from the one before us, none having the same origin. The tubers 

 of V. gongylodcs are formed by the special development of an 

 already existing stem ; and on this depends the interest of the case. 

 The branches of many plants would grow on accidentally fallin 

 to the ground ; but these tubers are endowed with special vitality, 

 and so prepared for intentional separation. I am unable to find 

 by inquiry at the Kew Herbarium that any case of similar kind 

 is on record. It is not described in the ' Flora Brasiliensis,' where 

 I believed there would be all the information of this plant in a 

 wild state. Ko mention is made in the manuscript notes of Bur- 

 chell, who collected the only specimens in the Kew Herbarium 

 near Para. 



Little requires to be said about the development of these tubers. 

 The onward growth is arrested; and the stem commences to 

 swell from about the last unfolded leaf backwards either one or 

 two nodes. Tubers of two swollen internodes are very common ; 

 and sometimes the swelling tapers off in some part of the second 

 internode from the point. The form is usually oblong, or tapering 

 from an obtuse apex to the base, with a constriction at the node 



CT 



