152 



THE INSTABILITY OF LEAF-MORPHOLOGY IN ITS 

 RELATION TO TAXONOMIC BOTANY. 



By a. a. Hamilton. 



In the ordinary routine-work of the Sydney National Her- 

 barium, parcels of specimens are received from horticultural, agri- 

 cultural, arboricultural, pastoral, and dairying districts accom- 

 panied by requests for information from the consignors. Farmers, 

 Stock-Inspectors, Shire Clerks (administering the "Noxious 

 Weeds Act"), Foresters, Secretaries of Agricultural Bureaux, 

 School-Teachers, and other correspondents who do not profess any 

 knowledge of systematic botany. As a consequence, the speci- 

 mens forwarded, in many cases, are examples in leaf only; and the 

 difficulty in determining such specimens, arising from the absence 

 of the definite characters exhibited by the flowers and fruits, 

 especially in the case of economic plants or those suspected of 

 poisoning stock, to which considerable responsibility attaches, 

 attracted the attention of the writer to the extensive range of 

 leaf-variation found within the limits of a species, and a corres- 

 ponding similarity in the leaves of distantly related plants. 

 While engaged collecting a series of specimens to illustrate the 

 ecology and xerophily of the strand-flora of Lady Robinson's 

 Beach, a change in the leaves of Senecio Unttus Forst., from 

 flaccid, thin, and entire, at a distance from the beach, to crass, 

 firm, succulent, and pinnatisect as the beach was approached 

 (13; 1913, p. 396), together with examples of Clematis ylycinoides 

 DC, exhibiting a gradual reduction of the normal trifoliate leaf, 

 to a simple one, occurring on an individual plant, {loc, cit.) 

 accentuated the impression already created. Attention was 

 directed to the subject in the field, and collections made, demon- 

 strating, for the greater part, the variation of leaves within a 

 species, and exhiV)ited from time to time at the Meetings of this 

 Society. A series of examples, chiefly Australian, most of them 

 familiar to local workers and readily available, together with 



