August 24, 1893] 



NATURE 



393 



it as qviickly as possible, especially the younger parts, 

 taking as much trouble over it as over the larvre. They 

 also cover it up again as soon as possible to protect it 

 from the light. A nest, i metre x 50 cm. was opened, 

 and in twenty-four hours the ants had put on a new roof 

 10 cm. deep. They also carry the nest with them upon 

 their migrations 



5. The Use of the Garden : its Construction and its 

 Tendance observed in Captivity. — Some ants' nests were 

 placed under a bell jar and supplied with leaves ; they 

 made no use of them and presently died. If they were 

 supplied with a piece of "garden," they rebuilt it and 

 covered it so far as they could. It was seen to shrink from 

 day to day, the ants bringing out the old pieces and adding 

 them to the wall ; finally it was exhausted and the ants 

 died. CUhers were starved for five days, and then sup- 

 plied with a bit of garden ; they at once began to eat the 

 Kohl-rabi clumps. It was found by this means that each 

 species of Atta will eat the Kohl-rabi of the other three as 

 well as its own. Finally, by supplying the ants with bits 

 of garden, a damp sandy floor, and fresh leaves, they were 

 induced to build in captivity. The dish in which they 

 worked was covered by a glass lid, and when this was 

 covered with a dark cloth or otherwise kept dark, the ants 

 built under it without covering the garden. In this way 

 the whole process was observed. An ant bringing in a 

 piece of leaf proceeds to cut it into halves, repeating the 

 process till it has got a very small piece left, which it 

 holds between its fore feet and turns round, crushing it in 

 its jaws until the whole is reduced to a round ball of pulp 

 about -25 mm. thick. This it then takes and adds to the 

 garden. So well is the kneading performed that no single 

 cell remains uninjured, and it was observed that the 

 hyphse of the fungus grew through and round one of these 

 particles within a i^vi hours. Belt supposed that this 

 process was performed by the small workers above- 

 mentioned, but it is not so, as we have just* seen. The 

 small workers perform the function of weeding the gar- 

 den, and this is so well done that a portion of it removed 

 and grown in a nutrient solution gives a perfectly pure 

 culture, not even containing bacteria ! 



6. De%ielopmcnt of the Fungus ajterremoval of the ants ; 

 the conidia, '^ pearl-hyphce" and strand-swellings. Result 

 of the artificial culture of the Fungus. — If a portion of 

 garden be left to itself in darkness, the ants having been 

 removed, aerial-hyphae develop in a thick mass several 

 centimetres high, with many anastomoses ; the Kohl-rabi 

 clumps are used up in the process, apparently supplying 

 material for it. The formation of conidia now takes place 



■■ all over the mass. From a hypha there buds out a lateral 



projection, which bears branches arranged roughly in 



whorls : upon these are again borne whorls of small club- 



, shaped branches, from whose ends are abstricted rows of 



I conidia, whose diameter is 2 ^t ; there are, as a rule, 



not more than ten in a row. Occasionally the formation 



I of the strings of conidia occurs not only on the final 



branches, but also on those of the preceding order. 



After the conidia are formed the mass collapses (about 



'the fifth day). 



' About the third day a careful search reveals among 

 ,the ordinary hyphas a itv/ which are covered, as with 

 jrowsof pearls, with small spherical lateral protuberances. 

 JThese " pearl-hyphae" arise from the ordinary ones. 

 |The cavity of the "pearl" is in direct communication 

 !with that of the hypha itself, and contains protoplasm. 

 |In connection with these there occurs a second type of 

 jconidia formation, distinguished by Miiller as the " weak " 

 jforrnation. There is no preliminary branching, the 

 conidia being abstricted from the ends of the pearl 

 jhyphae, or plain hypha; in connection with them. The 

 isnd of the hypha swells up and bears the conidiophores. 

 The chains generally consist of at least twenty conidia. 

 i Still a third form of hypha is to be found. Sooner or 

 1 ater there are observed on the garden thick white strands, 

 NO 124.3. "^OL. 48] 



which on examination are found to consist of hyphae, 

 which look like rows of beads, or yeast-chains, and are 

 much bent, branched, and twisted. From these there 

 arise pearl hyphse, or we may find pearls upon these 

 hyphffi themselves. These peculiar hyphse arise first of 

 all as "pearls" on ordinary hyphs, and then a process of 

 budding goes on, just like that which gives rise to yeast 

 chains. The " pearls" might be looked upon as homolo- 

 gous with these lateral swellings of hyphse, but there is 

 also another view, that they represent rudimentary 

 conidiophores. It has been seen above that the conidio- 

 phores in the " strong " conidia formation are not always 

 confined to the ends of the hyphas, but may at times 

 appear further back, and it is suggested that originally 

 they were borne anywhere upon the hyphse, and subse- 

 quently restricted to the tips, the "pearls" then repre- 

 senting rudiment.ary conidiophores. The " pearl " hyphae 

 and weak conidia formation are usually found in connec- 

 tion with these swollen strands, and on one or two 

 occasions a connection was found with the strong 

 conidia formation. 



When a few ants were left with a large piece of garden, 

 they did their utmost to prevent the formation of these 

 aerial hypha?, &c., biting them off as they appeared, but 

 gradually the fungus gained the upper hand of them. 

 Proceeding now to the results of culture in nutrient 

 solutions, the strong conidia germinate and give rise to 

 hyphse which ultimately bear strong conidia again. 

 Never did the " weak " form appear, but very often from 

 the main hypha there were given off lateral branches, some 

 of which developed into rows of beads, like the hyphas 

 described above, and others swelled up at the ends just 

 like the Kohlrabi. The cultures being pure, these for- 

 mations could not be pathological, produced by bacteria, 

 as is sometimes the case. 



Similarly the weak conidia gave rise only to conidia like 

 themselves. Pearl-hypha; were occasionally formed, and 

 rarely the peculiar hyphas like rows of beads. 



When one of these forms was grown in one culture 

 drop, and bent over into another drop, in which the other 

 form was, the two anastomosed freely, showing that 

 they belonged to the same plant. 



When a portion of Kohl-rabi is grown in the solution 

 it gives rise to ordinary hyphas, which ultimately produce 

 a new crop of Kohl-rabi. On one occasion it gave rise to 

 pearl-hyphas and weak conidia. 



To sum up, the fungus has two conidia forms, which 

 develop upon the garden in the absence of the ants. The 

 mycelium shows a strongly marked tendency to the 

 formation of swellings and protuberances, which appear 

 in a different form, more or less distinctly marked. One of 

 these, which has probably reached its present form under 

 the cultivation and selection of the ants, is the Kohl-rabi. 



7. Discovery of the Highest Fructification of the 

 Fungus. — It being evident that the fungus was either a 

 Basidiomycete or Ascomycete, attempts were made to 

 obtain its principal fructification by cultivation, but in 

 vain. A fortunate diicovery, however, was made of a 

 nest which had a huge red Amanita-Iike fungus growing 

 out of it. This was found to belong to the genus Rozites, 

 and the species was named A', gongylophora. The deve- 

 lopment of the basidia, &c., is given in detail, but need 

 not begone into here. Cultivation of the spores showed 

 that this was indeed the fructification of the Kohl-rabi- 

 forming fungus. 



10. Plants attacked by Leaf-cutting Ants. — These were 

 found to be very numerous, and no rule could be formu- 

 lated as to the operations of the ants. On one day they 

 would strip one plant and the next day leave it un- 

 touched, or vice versd. An interesting case was observed 

 in the cold weather. An army of leaf-cutters was found 

 stripping a Cecropia, though the latter was inhabited at 

 the time by its protecting ants ! The latter appeared to 

 be too numbed by the cold to go out and fight. 



