Taxonomic Anomalies 665 



gree of variability of its leaves. In some in- 

 stances these are one-bladed, the blade reaching 

 a length of 15 cm., and hardly resembling those 

 of the common bastard-acacia. Other leaves 

 produce one or two small leaflets at the base of 

 the large terminal one, and by this contrivance 

 are seen to be very similar to those of the Des- 

 modium, repeating its chief characters nearly 

 exactly, and only differing somewhat in the rela- 

 tive size of the various parts. Lastly real in- 

 termediates are seen between the monophyllous 

 and the pinnate types. As far as I have been 

 able to ascertain, these are produced on weak 

 twigs under unfavorable conditions; the 

 size of the terminal leaflet decreases and the 

 number of the lateral blades increases, showing 

 thereby the presence of the original pinnate 

 type in a latent condition. 



The sudden origin of this " one-leaved " 

 acacia in a nursery may be taken as a prototype 

 of the ancient origin of Desmodium. Of 

 course the comparison only relates to a single 

 character, and the movements of the leaflets are 

 not affected by it. But the monophylly, or rath- 

 er the size of the terminal blade and the reduc- 

 tion of the lateral ones, may be held to be suf- 

 ficiently illustrated by the bastard-acacia. It 

 is worth while to state, that analogous varieties 

 liave also arisen in other genera. The " one- 



