— 353 — 



parts instead of abruptly stopping to a considerable depth. The 

 darker dorsal vittae of such leaves are merely parts in which this 

 fully pigmented green tissue reaches out to the surface. 



Origin and Transmission. 



The physiological reason for the frequently marked pale ventral 

 stripe and conspicuous dark dorsal vittae shown by some species 

 in nature has not been ascertained. On the lava-beds of Naulingo, 

 where the type of the first named marginate Littaea (.4. lophuiifhd) 

 was observed, the typical form, nearly destitute of a ventral stripe, 

 and its striped form (A. nnioittafa) occur intermingled. A. LeclmjiiiUa 

 presents a pale form with very marked dorsal strlation, and the 

 more deeply colored form in which the vittae are but little darker 

 than the rest of the leaf, without demonstrated relation to environment, 

 though the plants of a given locality may produce the impression 

 of uniformity; and the paler form has been observed to assume 

 the darker coloration under lessened northern light intensity. 



It might have been supposed that the normally though imperr 

 fectly striped Littaeas, like these marginate species and A. pendula, 

 would have furnished most of the horticultural variegations. As 

 a matter of fact, however, aside from unioittafa, A. xijlonacantha is 

 the only one of either series that seems to have developed such 

 variegation, and in the former this is marginal while in the latter 

 species, though dorsal green lining is evident, normal ventral banding 

 is practically absent. 



The variegations, therefore, are apparently of causation in- 

 dependent of such normal beginnings, and this is no less obscure 

 than for the latter. Professor De Vries, considering leaf variegations 

 in general as at once among the commonest and least understood 

 of plant anomalies, holds them to be subject to environmental 

 influence, and liable to great Variation and continued reversion into 

 green or redevelopment from this normal coloration, both by seeds 

 and buds. 



As Korse hinskyi) has pointed out, the transmission of 

 variegations by seed, in Aj/aoe, has been too little tested to Warrant 

 very general inferences. Roland-Oosselin'-) found not a Single 

 variegation in thousands of seedlings raised from A. Miller i picfa 



') Flora. S5): 304. (1901). 

 ^) Rev. Hort 71: 254. (1899). 

 Wiesner-Festschrift 23 



