510 H. MAESHALL WARD. 



(h), the swelling up and passage out of the protoplasm took 

 place as usual : but the protoplasm was extremely small in 

 quantity and very watery. Large vacuoles at once became 

 formed, and the whole faintly granular mass soon fell to 

 pieces, merely becoming diffused, as it seemed to me, after the 

 bursting of the absorbent vesicle. These are undoubtedly 

 pathological phenomena, and cannot be considered as specific- 

 ally considered of the Pythium. 



As to the sexual organs and process of fertilisation, little 

 need be said here beyond calling attention to figs. 31 — 36. The 

 formation and structure of the oogonia and antheridia are 

 essentially as before ; and the passage of the fertilising material 

 through the tube (figs. 31a, 32, 33 and 34) needs no further 

 description — it takes place exactly as before described. 



The ripe oospore (fig. S6) presents the peculiar characters 

 of P. gracile (De Bary), especially in filling up the oogonium, 

 and I can select no distinguishing features between the two 

 forms, unless the peculiar knot-like groups of tuberosities and 

 the extensive extra-matrical growth, &c., be considered more 

 important than they seem to me.^ . 



It may be, however, that some confusion still- exists between 

 one or two forms with the simple zoosporangia of this type, 

 since, as De Bary points out,^ the P. gracile so closely studied 

 by himself is always a saprophyte, and refused to attack 

 Algse, whereas the earlier forms (P. reptans, De Bary and 

 P. gracile, Schenk) with which he seeks to identify it, were 

 found on living Algse. It seems probable that further research, 

 directed to enquire whether and how far the species named are 

 distinct, may yield important information as to the limits be- 

 tween parasitic and saprophytic tendencies; such research, 

 however, is likely to be valuable only so far as it is made on 

 carefully isolated cultures, observed during sufficiently long 

 periods. 



^ De Bary, however (' Bot. Zeit.,' 1881, p. 570), says the oogonia and 

 antheridia (of P. gracile) are found only iu the substratum, 'Nur im 

 Innern des Substrates, inter und intracellular.' 



2 ' Bot. Zeit.,' ISSl, p. 572. 



