THE LEAF. 



157 



observed by Dickson, which was growing in a pot and 

 produced a weak leafy shoot. To these two facts is 

 attributed the anomalous formation of well-developed 

 radical foliage-leaves, they, of course, being regarded 

 as transformed scale-leaves which alone are produced 

 in the normal plant. These foliage-leaves, to some 

 extent resembling the cladodes in size, shape, and 

 venation, differed from them in (1) the possession of a 

 distinct midrib; (2) the venation being convolute; 

 (3) being long-stalked ; (4) having the stomates on 

 the morphologically lower surface. These facts suffice 

 to show that these leaves were quite distinct organs 

 from the cladodes. Askenasy also observed the same 

 phenomenon in Danae racemosa, where well-developed 

 foliage-leaves were seen to follow on the green-tipped 

 sheathing scale-leaves at the extreme base of the shoots 

 sprouting from the rhizomes. That the foliage-leaf 

 represents the ancestral organ and the tiny colourless 

 scale of the cladode-bearing stem a later modification is 

 evidenced by the facts of ontogeny, for the seedling 

 always develops a number of ordinary foliage-leaves 

 subsequent to the cotyledons. There is no doubt 

 that cladode-formation stands in correlation with the 

 development of the leaves and bracts as minute scale- 

 leaves, and that the appearance of true foliage-leaves 

 represents a reversion to the condition of the plant 

 before it possessed cladodes. 



The runners or stolons of an enchanter's nightshade 

 (Gircsea intermedia) and a mint (Mentha aquatica) 

 were found, as described by Goebel, to develop small 

 foliage-leaves on exposure to light instead of the 

 minute scale-leaves normally formed underground. Yet 

 the runners of the moschatel (Adoxa moscliatellina) 

 under similar treatment could not be induced to form 

 foliage-leaves. 



The scale-leaves at the base of the stem of Anemone 

 Pulsatilla often develop a green blade and so become 

 foliage-] eaves. 



Lloyd cites a very interesting case in the yellow pine 



