PYTHIUM. 117 



sporangia, however, may tirst pass through a resting period. 

 Sexual reproduction consists in the impregnation of an e-.g-c.ell 

 by means of a fertilization-tube from an antheridium. The 

 oos pores are formed singly in each oogonium, and are liberated 

 only after decay of the oogonium \valls and the tissues of the 

 host-plant containing them. After a resting period they pro- 

 duce a germ-tube, which penetrates into the host-plant and 

 bt-ci- mies a delicate branched colourless intercellular mycelium. 

 Hibernation is accomplished both by these oospores and by resting- 

 vonidia, which remain amongst the decaying plant-debris on the 

 ground. 



Humphrey has observed sickness and death of cucumber 

 seedlings as a result of /'//. <l<- 7 /"///"///'///. \Vittmack found a 

 .species I /'//. X</</< ////"/////// ) very destructive on peas and lupines l 

 in various localities; it has been observed frequently since. 



Py. gracile is parasitic- on al^ar. 



Py. dictyospermum, I!a.-. m-curs in ,^/>i/-tj >//<(. 



Py. cystosiphon is found on specifs of /.//</<'. 



Py. intermedium fiv(|U.-nts pmtlialli cif vasi-ulai- c-i-ypti>uani^. 



Phytophthora. 



The mycelium is at first non-septate though much branched. 

 It grows linth between and through the host-cell<, and in si. me 

 -pecies, ('.//. /'//. omnivora), has small haustoria. 



Thf conidiophorea branch and produci- a lar-i- number of c.midia 

 or sporangia in succession. Tin- tirst conidia aiv in minal. but 

 are 'lisjilaced towards one side and thrown oil' by further 

 jrowth of the conidioph(re to pri'duci- nther conidia. 



The sporangia di>tribute, their contents as swarminu cells with 



twci lateral cilia: the c..nidi;i jH'oduce. a hypha dii'ecily. The 



-Cells are developed one in each c>< .-"ilium, ; md are I'ertili/.ed 



liy an antheridium. The sphei'ical OOSpores germinate in spring 



by means of a germ-tulie. 



Phytophthora omnivora, I > I'.ary- (syn. Ph. fagi, I.'. Hani-.) 

 This js ,i di-stnictivc enemy to the <ecd line's ( ,|' ciinileix. and even 

 more deadly amongst llRturally-SOWn beech-seedlings. healh .1 



the beech is preceded 1 >V 1 H'oW II -spc ,1 | j | p_. , ,)' MelllS, C( >1 V ledojis Mild 



1 I' /;/. /. Mij'.rktiltii,-. I MM. 



\'-. H:uii/, Z' i'^hrii'i i'. /'../' //. .lii'i'l </ * ,i 1^7".; .'1 i'*ii' 



'I. / llUt. Mniffl: ,, . I SNII. 



