158 DIFFERENCE OF ORGANS AT DEVELOPMENT STAGES 



Ridley 1 has pointed out that Pothos flexuosus, so much cultivated in gardens, 

 is in like manner the juvenile form of ' Anadendrum medium,' and we may 

 be the less surprised that this has not been noticed before seeing that in 

 this plant all its forms of leaf only seldom occur together 2 , and many 

 individuals persist for a long time in the juvenile stage. The forms of leaf 

 are represented in Fig. 97. The following is Ridley's description: 



A. The leaves are of a velvety green and stand in two rows close 

 together. If the plant grows higher they become broader and more ovate, 

 less oblique, cordate at base, and are evidently stalked and attain a length 

 of 7-5 cm. and a breadth of half as much. 



B. Still higher up they 

 attain a length of 18-20 cm. 

 and a breadth of 10 cm., 

 develop a long point and a 

 short thick stalk of 2-5-4 cm. 



C. We next find them 

 still in two rows and lying 

 flat upon the stem of the 

 supporting tree, but now they 

 have become pointed ovate 

 with a cordate base, and are 

 15-20 cm. long" and 10 cm. 

 broad, with a stalk i o cm. long. 



D. The distichous ar- 

 rangement is now lost and the 

 leaves no longer lie upon the 

 stem but spread out in all 

 directions ; their dark shining 

 green shows that they are very 

 different from the delicate 

 velvety green leaves of the 

 lower region, and whilst the 



outline and size of the preceding leaves are retained, indications appear 

 of feathered segmentation. 



E. The stalk has now a length of 20 cm. and forms a 'knee' close 

 to the lamina, which latter has a length of 20 cm. and is cut in a feathered 

 manner almost to the midrib, whilst on both sides of the midrib a number 

 of elliptic perforations are found. 



F. The lamina of the leaf has attained now a final length of over 



FlG. 97. Anadendrum medium ('Pothos flexuosus'). Different 

 forms of leaf. A unstalked ' velvety leaves' ; B thicker leaves 

 from higher up the stem ; C the leaf-stalk now begins to appear; 

 D-G further stages of differentiation, Gis a leaf from a flowering 

 plant ; H leaves of a ' stolon.' 



1 Ridley, in Gardeners' Chronicle, ser. 3, vol. i (1894), p. 527. 

 - In the aroid figured in Fig. 95 this commonly happens. 



