122 Kelly, On the Fimction of Acacia Leaf Glands. [v'oT^xx^ 



munication — not, in fact, a nerve : nor is it attached to 

 responsive contractile tissue. Having quarrelled with this 

 terminology, I began to have my doubts as to other terms, and 

 the next was " gland." I doubted whether these excrescences 

 were glands at all. To satisfy myself on this I have searched 

 through many books and examined many species of acacia, 

 and these peculiar structures in situ and in section with lens 

 and microscope. Before I had examined half the number of 

 species mentioned and figured by Mr. Hardy I was impressed 

 with his patience and accuracy, and was surprised also to find 

 that in Strasl:)urger (4th Eng. ed., 191 2) there is no mention 

 of glands in respect of these or any other plants, and the word 

 is not even indexed. It is still more interesting to find on 

 page 168, figure 174, depicted a seedling of Acacia pycnantha 

 with phyllodes bearing nectaries. These ''nectaries" are 

 undoubtedly identical with the glands, and the word " nectary " 

 is more confirmative of a gland-like nature than even gland 

 itself. The term is usually associated with the flower, but there 

 are undoubtedly leaf nectaries. These are distinguished by some 

 authors by the term " extra-floral nectaries." Prior to seeing 

 tliis illustration, I was firmly of the opinion that, whatever the 

 function when on leaves, they were mere survivals, obsolete 

 and functionless, on phyllodes. I then went in search of facts, 

 and in the large number of glands examined could not find, 

 even with the microscope, any secretion of a nectar or liquid 

 nature. Uncut, they appeared to be firm, hollow, warty 

 excrescences, with a central aperture protected by fine hairs. 

 Sectional] y examined, the cavity was empty, with a hard, dry, 

 inner wall, hung with most beautiful, minute crystals — a 

 veritable stalactite cavern. The material was fresh from the 

 trees, but these were not in flower. The only acacia I could 

 find in bloom then (March) was the Natal Wattle, Acacia 

 Natalitia, a pinnate-leaved species bearing a glandulous growth 

 between each pair of pinn«. In none of this species could I 

 find any nectar, and the best in that respect that can be said 

 of these glands is that they were more succulent or less dry, 

 and more warty in appearance, than those of other species. 

 It is significant that, in keeping with what Mr. Hardy says — 

 viz., that these growths appear early in the development of 

 the leaf — they also become hard and shrunken as the leaves 

 become older, and brown, red, or purphsh, approximating to 

 the colour of wattle-bark, and practically dead in the oldest 

 leaves. This fact may indicate that the gland, or the organ 

 of which it may be only a relic, belongs to a comparatively 

 early stage of the race history of the genus. Whatever its 

 function, it is active only in the first two seasons, possibly only 

 in the first. Another fact is that in pinnate leaves the glands 



