BY J. J. FLETCHER AND C. T. MUSSON. 203 



The difficulty which confronts anyone who tries to interpret 

 the axillary, bulbous swellings of seedlings of Eucalypts, whether 

 Mallees or not, and Angophoras, from the standpoint that the 

 Mallees have rootstocks, is exemplified by the following quota- 

 tion from a recent paper by Dr. Hall* — "The origin of the 

 peculiar rootstock of the Mallee can be well seen by observing 

 the seedling. In nearly all the Eucalyptus seedlings, and also 

 in the Angophoras, there is developed, especially if growth is 

 checked, a small woody swelling in the stem at the point of 

 attachment of the cotyledons. A number of buds will develop 

 on this, and shoots start from them. Jf the growth of the seed- 

 ling proceeds in the form of one main stem, this swelling is soon 

 obliterated, but, in the Mallee, these secondary shoots grow 

 almost as quickly as the main stem, and so, instead of a tree in 

 the ordinary sense, we have an enlarged rootstock, from which 

 spring numerous stems, all more or less of the same size." The 

 author is here trying to explain Tate's problem of the transient 

 and persistent basal inflations of the Non-Mallees and the 

 Mallees. If the small woody swelling at the attachment of the 

 cotyledons of the seedlings of Mallees is the initial stage in the 

 formation of a persistent rootstock, is not the woody swelling of 

 the seedling of Non-Mallee Eucalypts and Angophoras also the 

 initial stage in the formation of a transient rootstock ? 



The following statement from Tubeuf and Smith's "Diseases 

 of Plants" (p. 299) may be mentioned. " In the Botanic Garden 

 at Amsterdam, the roots of several species of Eucalyptus ex- 

 hibited woody tumours from which proceeded outgrowths re- 

 sembling 'witches' brooms.' 'J hese contained the mycelium of 

 an Ustilago which produced spores in the cortical tissues." If 

 the tumours here referred to are of the same kind as those we are 

 interested in, we consider that the presence of Ustilago under 

 the circumstances mentioned, is to be regarded as merely in- 

 dicative of a saprophytic intruder. As pointed out by Erwin 

 Smith and his colleagues, a varied assortment of lodgers com- 

 monly infest crown-galls. 



* "The Evolution of the Eucalj^pts in relation to the Cotyledons and 

 Seedlings." These Proceedings, 1914, p,ol7. 



