RHIZOPUS EOT OE STRAWBERRIES IN TRANSIT. ( 



PHYSIOLOGY OF RHIZOPUS NIGRICANS. 



CHARACTER OF THE ROT PRODUCED. 



The rot produced in strawberries by Bhizopus nigricans differs 

 from that caused by any other organism the writers have observed 

 and has been briefly described in an earlier paper (13). Its chief 

 characteristic is the rapid collapse of the berry, with the loss of 

 much juice. So great is this loss that the juice often drips from 

 boxes or crates containing strawberries rotted by Rhizopus, and this 

 has given rise to the name " leak " applied to this type of rot by ship- 

 pers and dealers. F.' L. Stevens (12) has recognized Rhizopus as 

 the cause of this type of rot in strawberries. 



HUMIDITY RELATIONS. 



In investigating the humidity relations of this fungus in its attack 

 on strawberries, a method already described by one of the writers (14) 

 was employed. Briefly, the method consists in using a series of desic- 

 cators filled with mixtures of sulphuric acid and water in various pro- 

 portions. From the specific gravity of the acid the relative humidity 

 and the saturation deficit of the air in the desiccator were calculated. 



Repeated experiments, using partly decayed berries received in 

 shipment, as a "Ml as sound Klondikes and Missionaries inoculated 

 with Bhiz6p nic] 'nigricans, proved that the fungus will destroy the 

 strawberry '* ne $i\ckly in a very dry atmosphere, even under concen- 

 trated sulpiP e Facid, as in a moist or saturated atmosphere. Certain 

 differences in~the attack of the fungus on the berry under various 

 humidities have been noted (13). The important fact in this con- 

 nection is that when the fungus is once inside the strawberry no 

 amount of external drying is sufficient to stop its development. The 

 moisture contained in the fruit will permit the fungus to grow suffi- 

 ciently to destroy the berry. 



TEMPERATURE RELATIONS. 



The temperature relations of Bhizopus nigricans have recently been 

 studied by two investigators. Hanzawa (8) studied die temperature 

 relations of various species of Rhizopus and used these relations as 

 criteria for separating the genus into sections. He places Bhizopus 

 nigricans in the section characterized by having no growth at 37° C. 

 (99° F.). He found that this species was able to grow and produce 

 sporangia at temperatures as low as 8° to 10° C. (46° to 50° F.). 



Miss Ames (1) included Bhizopus nigricans among the storage-rot 

 fungi whose temperature relations she investigated. She found that 

 at 9° to 10° C. (48° to 50° F.) some growth occurred, although at 

 this temperature the fungus was unable to mature sporangia within 

 one month. Maximum growth occurred at 36° C. (97° F.), good 

 growth at 37° and 40° C. (99° and 104° F.), and no growth whatever 



