April, 1910,] 



327 



Plant Sanitation. 



months old culture ou cacao-bark, 

 namely, pustules of Fusarium conidia. 



Hanging drop-cultures of these Fusa- 

 rium conidia were started, so that the 

 development could be watched under 

 the microscope. In water no conidia 

 were produced, but a saccharose-solution 

 of \ % appeared to be suitable. In it the 

 Fusarium conidia always gave rise to a 

 mycelium which produced conidiophores 

 of Spicaria. 



The converse question now arose, 

 namely, whether Spicaria could produce 

 Fusarium. To study this, I made hang- 

 ing drop cultures of Spicaria-comdi&. 

 These nearly always developed a myce- 

 lium which produced the Spicana- 

 fructification, but in rare cases the 

 mycelium formed a conidiophore with 

 Fusarium conidia. 



In several ways I tried to obtain a 

 higher fructification ; I made cultures 

 in large flasks and dishes on sterilized 

 bark, wood, bread, or liquids ; I let 

 some grow very old, put others into the 

 light or kept them in the dark, but with- 

 out any success. In old cultures on 

 cacao-bark I sometimes did find small 

 hollow bodies, from which, when pre&sed, 

 numerous oil drops escaped. As several 

 species of Nectria possess two kinds of 

 conidia, microconidia and a Fusarium, I 

 do not think it unlikely, that in this case, 

 too, the higher fructification will prove 

 to be Nectria, of which the little globules 

 perhaps form the first development. 



I have named the species Spicaria 

 colorans- 



I have not succeeded in producing 

 canker in cacao trees by inoculating them 

 with Spicaria. I introduced small pieces 

 of sterilized bark or wood, which had 

 been permeated by the fungus, into 

 small wounds, which had been cut in 

 the bark of the trees, or between bark 

 and wood, and kept these places moist ; 

 I experimented in the same way witli 

 conidia of Spicaria or of Fusarium. Nor 

 was infection induced by bringing 

 conidia of Spicaria or Fusarium on 

 uninjured bark. Experiments in which 

 pieces of diseased bark were introduced 

 into wounds of healthy trees likewise 

 failed. This failure accordingly does 

 not prove anything against Spicaria 

 being the canker parasite, but leads to 

 the conclusion, that the conditions which 

 rendered the trees susceptible to the 

 disease, or which are necessary for secur- 

 ing the infection, were not present. 

 Attempts to infect fruits likewise failed. 



After this discussion upon the canker 

 parasite I think it advisable to deal with 

 some saprophytes, one of which at least 



very often occurs on canker trees. It is 

 a Nectria which I at first supposed to be 

 the cause of the disease, the more so as 

 in Ceylon and elsewhere a Nectria is 

 regarded as such. Moreover, nearly 

 always the same form occurred. It was 

 therefore grown in pure cultures. The 

 bicellular spores were sown in hanging 

 drops; they germinated readily and 

 produced a mycelium with Fusarium- 

 conidia. A comparison of this Fusarium 

 with the one produced by Spicaria 

 makes it clear at once, that it is a form 

 differing from the above described 

 parasite. 



1. The shape is different in several 

 respects :— 



(a) Fusarium from Spicaria is more 

 curve i than iheone from Nectria. 



(b) the ends of the former are rather 

 sharply pointed, those of the latter 

 always very obtuse ; 



(c) the former alone often bears a small 

 stalk which is sometimes bent at 

 the place where it was formerly 

 joined ; 



(d) the contents of the former are much 

 more coarsely granulated than 

 those of the latter. 



(e) moreover the dimensions of the 

 former are smaller ; 



2. -Fwsarmm-conidia which originate 

 from Spicaria, always produce 

 Spicaria ; Fusarium-conidia, from 

 Nectria on the other hand never 

 yield anything else than Fusarium. 



3. Their different character is also 

 shown by their mode of growth on 

 nutrient media. On a slightly alka- 

 line medium, colonies developed from 

 (Spt'carin-Fusarium assume a red 

 colour, those from iVecfrm-Fusarium 

 do not. It is evident from the 

 differences enumerated that this 

 Nectria is not a fructification of 

 Spicaria, the canker parasite. 



Probably we have to do with Nectria 

 striatospora, Zimmermann, which was 

 found by Zimmermann on cacao trees at 

 Buitenzorg, and which he also considered 

 as probably harmless. 



As has already been said, Nectria is 

 considered to be the cause of Canker in 

 all countries where the disease has been 

 observed. 



On a number of diseased patches 

 Carruthers found pustules of small, 

 oval, unicellular conidia ; after some 

 time larger, multiseptate, crescent-shap- 

 ed conidia appeared, and at last perithe- 

 cia of Nectria. Fi om this he concludes 

 that Nectria is the canker parasite, and 

 that both forms of conidia are stages 

 in its life-history. This conclusion, how- 



