Vou XIV, No. 11 -Botanical Gazette -Nov., 1889. 



A new AmericaD Phytophthora. 



ROLAND TIIAXTER. 



The Lima beans in the vicinity of New Haven, within a 

 radius of at least fifteen miles, have been subject during the 

 present season to a serious disease resulting from the attack 

 of a species of Phytophthora, quite different from the com- 

 mon P. infestans both in its general appearance and micro- 

 scopic characters. The disease was first observed earlv in 

 September, in the town of Hamden, where it was causing 

 great damage in "truck" gardens, resulting in the destruc- 

 tion of a large percentage of the crop. The pods at differ- 

 ent stages of maturity furnish the favorite point of attack, 

 although the fungus occurs frequently on the young bean 

 shoots, and sometimes, but more rarely, upon the leaves and 

 petioles. On the pods it appears as a clear white felted coat- 

 ing, covering them entirely or forming irregular patches 

 extending usually to both surfaces. The young shoots, al- 

 though often considerably swollen and distorted, were found 

 to contain no oospores; neither were the latter observed in 

 any of the pods examined. The disease spreads rapidly. 



like its congener, and the pods, soon after the Phytophthora 

 has appeared on any part of them, fall a ready prey to vari- 

 ous saprophytic forms. Cladosporium, Epicoccum, etc., which 

 complete their destruction and cause them to turn black. 



The conidia are much larger than those of P. infestans 

 and usually broader in proportion to their length. The con- 

 idiophores are also different in their appearance and mode 

 of branching. I was unable to observe the maximum num- 

 ber of zoospores formed in germination ; but spores of aver- 

 age dimensions produced from fourteen to sixteen. In a few 

 cases a simple germinal tube was observed, but far more 

 rarely than in P. infestans, while the production of second- 

 ary conidia as a result of lateral or terminal germination 

 was also seen in a number of cases. The conidiophores are 

 very common! v quite simple above their point of exit through 

 the stomata ; but more often arise two or more from a com- 

 mon, slightly swollen, base, above which they may be sim- 

 ple or once diehotomously branched. During long continued 



