KXl I.rUKl) Sl'KHES 



35 



('()(>) also r»-|)ortf(l that /'. Calif iiruiae is not an or- 

 K.-iiiisin Init only (Icjicntratfd cliloroiiliyll. and in 

 IJ>0!l .Main- and Tison conliniud the (indinys of Imtli 

 of tlu'sc in\ (stiirators. 



P. ORCHIDIS MasMO. l!>!)j. Ami. Bot. !): 170, IJl-U'i), 

 1>1. 1."). 



L'ndir this nanu- Ma.ssec reported an organism 

 whieli lie believed to be tlie cause of spot diseases of 

 orehid leaves. Later in the same year after more in- 

 tensive stndy he retracted this view and sliowed that 

 what he had previously believed to be s))ores were 

 nothing more than tannin vesicles. 



P. TOMATI .\l)l»y. IWI."). .lour. Hurt. M-A ser. 30:.%a. 



.Vbliey st.ited in a letter to the .lourii;il of Horti- 

 culture tiiat this organism is probably the cause of a 

 disease of tomatoes, but as far as the present writer 

 is aware he never gave a description of the parasite. 

 Massee ('9.5, p. 427) believed that Abbey's disease 

 is not due to a ))arasitic organism but to certain rapid 

 changes in environmental conditions. 



P. HUMULI Kirk. lS()(i. Utpt. Dept. Agric. New Zealand 

 11: 337. 



On the roots of hops in New Zealand Kirk found 

 galls which were similar to those produced by P. 

 Brassicae on crueifcrs. and without seeing the causa- 

 tive agent, he assumed the disease to be caused by a 

 species of Plasmod'tophora to which he gave the name 

 P. huniuli. In 1922 Nicholls reported a disease of 

 hojis in Tasmania which showed the "take all " symp- 

 toms, and he assumed it to be caused by the same 

 organism without examining the tissues microscopi- 

 eally. Later, in his correspondence with Miss Mc- 

 Lennan ('31. p. 12) he stated that he had found a 

 mvxoniycete which he took to be P. humiili. In study- 

 ing the "take all" disease of hops more intensively 

 in Tasmania, McLennan concluded that it may be 

 caused by a virus. In some of the diseased plants, 

 however, she found a })lasniodial organism which 

 was later isolated and grown in pure culture and 

 turned out to be a proteomyxean species. Leptomyxa 

 reticulata var. hiimuli. .She also examined preserved 

 material of diseased hops labelled 1'. humiili which 

 belonged to the Department of .\griculture, Mel- 

 bourne, but found no evidence of a myxomycete. Miss 

 McLennan accordingly concluded that tiie tumors 

 described by Kirk were crown galls caused liy Pseii- 

 dnmonas tumrfacicns and that P. huniuli is no longer 

 valid. 



P. VASCULARUM Matz, lO.'O. .Jour. Dcyit. Afrric. Porto 

 Kifo J: I.), fi(:s. 7-9. 



Liiniifra rn»rulnrum M. T. Cook, Ifl.'B. Ihiil. 13: l!t. Pis. 



3-6. 

 Soroiiphaera vimculiirum M. T. Cook. 1937. Ihiil. :31:S1. 



Pis. 5-7. 



This species was described by Mat/. ('20, '21, 

 '22) as causing the dry top rot of sugar cane, Sac- 



fhanim officinal i, in Porto Hieo. and in lilSl it wa.s 

 re))orted on the s.ime liost in \'ene/,uel;i by Chardon 

 .ind Toro. .M . '1'. Cook triiusfcrred the org.-inisin to 

 the genus Lii/nicra because it does not cause hyper- 

 trophy of the host. Later ('32), W. R. I. Cook m.adc 

 an intensive study of the organism from material 

 sent by M. T. Cook and found that the disease was 

 caused by two protozoan ))arasitcs to which he gave 

 the names Amocbo.iporus t'asculariini .uid ./. Sac- 

 charinum. M. T. Cook later ('37) tr.insfcrrcd it to 

 the genus Snro.s'pliarra. 



P. TABACl Jones, 19-'(>. I?ot. Gaz. xl: Uli, pis. 31-37. Kig. 

 1. -'. 

 /'. lulu, cum .Tones, Ifl.'fi. Pliytopatb. Ifi: fi7. 



In tobacco. |)otato and tomato plants ati'ected with 

 mosaic-like symptoms and leaf roll, Jones found a 

 plasmodiaceous organism which he believed to be a 

 species of Plasmodiophora. Infected cells become 

 necrotic and adjacent ones hyperplastic, and all tis- 

 sues except bast fibers and xylem are invaded by 

 ))lasmodia which pass from cell. .lones found only 

 Plasmodia in the host plants, but when these are 

 cultured in Knop's solution, they give rise to amoebae 

 and uniflagellate organisms, both of which may or 

 may not encyst. The amoebae which eontiiuie to de- 

 velop discharge ehromidia from the nucleus into the 

 cytoplasm, and these chromidial bodies soon aggre- 

 gate to form daughter nuclei, thereby making the 

 enlarged amoebae multinucleate. Such amoebae give 

 rise to motile uniflagellate isogametes which fuse 

 shortly, forming a uniflagellate zygote. The zygote 

 then divides into two zoospores which in turn form 

 amoebae. 



The flagellate cells and amoebae which encyst pro- 

 duce amoebae on germination, and these fuse to form 

 the Plasmodium. According to .Tones, hundreds of 

 amoebae may flow together in this manner and make 

 a huge Plasmodium which creeps along ra})idly like 

 a giant amoeba ingesting food in its path. S])orogen- 

 esis in this species is unlike that of any known mem- 

 ber of the Plasmodioi)horaceae. As the ])lasmodium 

 moves along, oval and s|)lierieal sjiorcs are delimited 

 in rows and left behind. The nuclei of these spores 

 soon enlarge, discharge chromidi.i. and eventually 

 disappear, while the ehromidia in the cytoi)lasm ag- 

 gregate and form daughter nuclei. Walls develop 

 around these nuclei, and in this fashion 3 to 15 

 endogenous spores are formed. Plasmodiophiira ta- 

 haci has a very complex life history, according to 

 .Tones, but he was not certain as to the sequence of 

 stages. Since he also found cert.-iin flagellate and 

 amoeboid stages which could not be fitted into any 

 known life cycle, it is not ini])robable that he may 

 have had more than one organism at hand. Miss Mc- 

 Lennan ('31) believed that the plasmodial stage 

 may relate to a proteomvxean-like organism of the 

 Lcpfnmi/ja reticulata type. In IStSI Cook expressed 

 a similar opinion in st.iting that P. iahaci is prob- 

 ably a species of amoeba which had temporarily en- 

 tered the tobacco leaf, but in 1933 he suggested that 



