6 Vegetative Organs. 



considered as a morbid enlargement of the affected part of the plant, due 

 to ; agency (Connold 1 ), then there need be no hesitation in calling 



those structures galls. 



Perhaps the most striking illustration of a gall is seen in Uromy- 

 dadium tepperianum. In the neighbourhood of Melbourne hedges of Kan- 

 garoo Acacias (A., armata} are being gradually and completely destroyed by 

 the ravages of this fungus, which resemble on a superficial view large galls 

 caused by insects. Most of the branches, including the phyllodes, are 

 infested with the chocolate-brown swellings, which may be in the form of a 

 succession of small excrescences about the size of peas, or collected into 

 large clumps about the size of walnuts, and measuring 4 cm. across. In 

 some cases they are solid round knobs, and the external appearance is due 

 to the dense covering of the chocolate -brown teleutospores. One of the lar- 

 gest was met with at Myrniong on Acacia implexa of an irregular leg-of- 

 mutton shape and weighing about 3 Ib. (PI. XLI). 



On A. pycnantha, or Golden Wattle, the galls are as large as potatoes, 

 and in some of the wattle plantations, where the trees are cultivated for 

 tlv-ir bark, they hang in large numbers from the branches like so many 

 fruits, and numbers of the trees are either dying or dead. The swellings 

 are primarily caused by the fungus, and then various insect larvae may 

 ultimately invade them, boring and tunnelling through them. In A. implexa 

 the swellings may run along the whole length of the elongated phyllodes, 

 and in A. salicina there is an all-round swelling of the branches, and the 

 periderm is ultimately ruptured. Magnus 3 found the galls to be per- 

 meated by an intercellular mycelium, which was multiseptate with numerous 

 and somewhat branched haustoria. 



Some very large galls were also found on the Black Wattle (A. decur- 

 rens} and Silver Wattle (A. dealbata} either surrounding or terminating the 

 branches, and caused by U. notabile. Some measured 4-5 inches across, 

 and 3-4 inches was not uncommon, while one of the largest weighed is cz.' 



The i>eculiar gall-like swellings caused by Gymno sporangium may be 

 mentioned, the mycelium of which is perennial in the various species of 

 Juniper, and from their appearance are popularly known as " cedar 

 [ in America. It may be an annual gall only bearing the teleuto- 

 spores for one season, or a perennial gall, producing- successive crops of 

 teleutospore:? year after year, and not requiring the transfer of the spores 

 each 



Localr.cd M ycdhtm. The localized mycelium may likewise produce 

 conspicuous swellings, particularly on the stem and midrib of the leaves 

 Thus, that of Aecidinm urticae causes hard curved thick swellings of con- 

 siderable extent, and such a development of starch takes place in some 

 Jimalayan species of nettle attacked by this fungus that the natives eat 

 the overgrown and hypertrophied stems for food. 



In other cases the affected tissues may be so stimulated bv the localized 



mycelium as to cause their death Thus almond leaves have been found 



, riddled w.th "shot-hole." due to the mvcelium of Pucdnia 



prum Pers just as P. malvacearum may also destroy a circumscribed 



. and falls Out, 



e mycelium, whether localized or perennial, is always beneath the 

 surface of the plant and formed within the living tissues. It 's delicate 

 in texture. l,ke all mternal mvcelia, and branches to form a regular Vet 

 work ultimately forming compact cushions or spore-beds. It can often be 

 traced from a ungle point of infection, whence it radiates all round and 

 spreads, gathering matem! for the fresh production of spores 



