FusARiA OF Potatoes 



223 



The organism was isolated from a flexible, semi-soft, rotted potato 

 tuber late' in the spring. No other organisms were associated with it. 

 Very similar organisms were isolated also from discolored fibrovascular 

 bundles of potato tubers from various States. 



Average measurements of the conidia from four different cultures are as 

 follows : 



Conidia: 0-septate, 52.5 per cent, 7.9 x 2.6/x 

 1-septate, 8 per cent, 15 x 3.1/i 

 2-septate, rare 



3-septate, 39 per cent, 34 x 4 (32-36 x 3.8-4.2) /x^o 

 4-septate, 0.5 per cent, 37.5 x 4.35/i 

 5-septate, very rare, 37.5 x 4.35ju 



Chlamydospores (on corn meal culture one hundred and seventy-three 

 days old) : 



0-septate, in conidia, 7.7 x 7 (6.5-11 x 5-8) ^t . 

 0-septate, in mycelium, 9x8 (7-11 x 5-8) ^ 

 1-septate, in mycelium, 14 x 9.5 (11-16.5 x 7-13.4) ^^^ 



Fig. 36. — Fusarium oxysporum var. longiiis. a, Pseudopionrwtal conidia from 21-days-old 

 cidture on slightly acidified hard potato agar; b, conidia from I^G-days-old culture on red racp- 

 berry cane plug; c, pseudepionnotal conidia from 5-days-old hard lima-bean agar; d, sporo- 

 dochial conidia from 36-days-old culture on oat agar; e, pseudopionnotal conidia from 22-days- 

 old culture on corn agar; f, conidia from 202-days-old ctdture on potato stem plug; G, conidio- 

 phores from 46-days-old culture on red raspberry cane plug; H, conidiophores from 5-days-old 

 culture on hard lima-bean agar; i, chlamydospores from 202-days-old culture on potato stem 

 plug 



5° Variation of averages of at least ten spore measurements. 

 5' Variation of individual spore measurements. 



