Chap. VI] 



ANIMALS 



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Thus prepared, the now shapeless little masses are worked up into a 

 coarsely porous spongy mass which fills the interior of the nest and 

 forms the fungus-gardcii (Fig. 73). The little masses, the initial green 

 olour of which changes first to bluish-black and finally to yellowish- 

 brown, are traversed in all directions and bound together by fine mycelial 

 :hreads. On closer inspection, innumerable little white bodies, at the 

 •nost -5 mm. in diameter, may also be seen ; they spring laterally from 

 he mycelial threads and arc termed by Moller 'kohlrabi-clumps' (Fig. 

 ,■4). The)' consist of an agglomeration of short branches with node- 

 ike or globular swollen ends and very rich protoplasmic contents. Tlic 

 kohlrabi-clumps ' are the most important if not tlic sole food of tJie ants, 

 vid represent a new structure, zvkick has arisen as a result of artificial 

 election exercised by the ants. 



The 'kohlrabi-clumps' appear very early in the fresh masses and 

 hen disappear, when these assume a brown colour. Alf. Moller has, 

 )y ingenious experiments, revealed 

 he whole workings of the ants in 

 heir fungus-gardens, and has shown 

 lOW the tiniest female workers keep 

 )ff all foreign organisms, so that 

 I'ithout further trouble the little 

 nasses can be used for pure cul- 

 ures, and how the ants, by indus- 

 riously biting off the subaerial 

 hreads, prevent the vegetative 

 prouting which will be described 

 jrther on. He has also directly 

 bserved, in numerous cases, the 

 ctual eating of the ' kohlrabi- 

 lumps' and has proved that in their absence the ants die of starvation. 



The fungus, as a rule, remains in the purely vegetative condition 

 lat has just been described. Only exceptionally, and under unknown 

 onditions, do large pileate sporophores of a purely agaric type develop 

 'om the mj'celium and crown the top of the ants' nest, a feature that 

 ■■ all the more striking because large pileate fungi are rare in tropical 

 lin-forests. Such discoveries have made it possible for Alf. Moller to 

 etermine exactly the systematic position of the fungus, and to describe 



as a new species of the genus Rozites, R. gongylophora, Moll. 



The four species of Atta that occur near Blumenau cultivate the same 

 pecies of fungus, which is never found outside the ants' nests. We have 

 lerefore here a highly developed case of reciprocal adaptation between 

 nlike organisms. 



The removal of the ants from the fungus-garden results, after a few 



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Fig. 74. 'Kohlrabi-chimps' of Rozites gongy- 

 lophora, Sloll., the fungus of the South Itazilian 

 species of Atta. Magnified 150. After Alf. Moller. 



