37 



OIM THE METHOD OF GROWTH OF THE 

 CONIDIAL CLUSTERS OF TRICHOTHECIUM 



ROSEUM. 



By Jessie S. Hayliss FAlioii, I). Sc. liirm., B. Sc. Land. 



On examining a dense mass of Trichothecium roseum 

 wliich had been growing for some months on decaying vine 

 leaves in a moist chamber, I came across what at first I 

 thought was an abnormal method of conidia formation. 



Crowning the tops of most of the conidiophores were 

 dense racemes of conidia, more or less pendulous (fig. la), 

 instead of the usual clusters (fig. ib); some of the racemes 

 were as long as the erect hypha bearing them. 



The conidia were not inserted on an axis as anticipated 

 but each conidium except the terminal one was attached to 

 two others and thus a long raceme-like chain was formed 



1 he method of growth is peculiar and is basipetal ; each 

 conidium including the first arises oblicjuelv (fig. 3a) some- 

 times even horizontally at the apex of the conidiophore, this 

 is cut off from the conidiophore by a cell wall, and beneath 

 the cell wall the hypha swells out into another conidium 

 also obliquely placed and opposite the other one, but still 

 attached to it (fig. 3b) and in its turn, it becomes cut off and 

 so the process continues (fig. 3), conidia one after another in 

 a close spiral being produced by the swelling out of the 

 apex of the conidiophore; and thus a chain is produced in 

 which each conidium is attached to two others, and of which 

 the terminal conidium is the oldest, and the one the most 

 recently formed is at the top of the hypha. 



The various stages are easily followed in a small culture 

 made in a hanging drop. 



Under ordinary circumstances only a verv short raceme or 

 chain is produced, and this has evidently been mistaken for 

 a head of conidia, because the conidia are verv crowded 

 together ; but it has the same basipetal method of form- 

 ation and the conidia are not inserted as they are usually 

 figured — at the same level on the top of the conidiophore. 



Under the favourable conditions of growth in a still, warm, 

 moist, covered culture chamber instead of the usual small 

 cluster of conidja or apparent head, a long pendulous 

 structure is formed. 



