MR JOHN RATTRAY ON ECTOCARPUS. 599 



from the same gathering, which were kept in a somewhat colder part of the 

 " Ark," did not discharge them so soon as others which were placed in the micro- 

 scopic room, which was kept at a higher temperature. 



It is, moreover, interesting to observe, that although the septa across the 

 multilocular sporangia of Ectocarpus siliculosus usually persist, yet it sometimes 

 happens that these septa disappear before maturation of the spores, in which 

 case the sporangium becomes ultimately unilocular. 



This observation corroborates the statements made by Peingsheim * with 

 regard to Ectocarpus siliculosus and E. granulosus, whose general conclusion 

 is stated as follows : — " Diese Beobachtungen fiihren zu dem Schlusse, dass 

 die DifFerenz der beiden Sporangienformen der Phaeosporien, die sich in der 

 fehlenden oder vorhandenen Facherung ausspricht, keine absolute ist, sondern 

 nur einen verschiedenen Grad der Ausbildting und Persistenz oder Resorption 

 des transitorischen Mutterzellgewebes der Schwarmsporen ausdriickt. Bei den 

 Oosporangien geht dasselbe der Regel nach schon gleichzeitig mit der Reife 

 der Zoosporen zu Gruncle und persistirt nun in einzelnen Fallen; bei den 

 Trichosporangien bleibt mindestens der altere Theil des Mutterzellgewebes 

 gewohnlich stehen, wahrend die jiingeren Generationen — ob immer ? — zu 

 Grande gehen; aber in einzelnen Fallen wircl auch hier das ganz Mutterzell- 

 gewebe resorbirt und dann erscheinen die Trichosporangia wie uniloculare 

 Organe." 



Although conjugation between the escaped swarmspores of the multilocular 

 sporangia was carefully looked for, no instance of it was detected. GoEBEL,t 

 however, has already pointed out that such swarmspores conjugate during 

 summer, when two neighbouring sporangia burst simultaneously. Probably 

 the inertness induced by the lower temperature of the watery medium in 

 December was enough in itself to check any such reproductive process. 



Although in most cases specimens of Ectocarpus siliculosus which were 

 affected with parasites did not bear true normal reproductive organs of any 

 kind, I have, in one case, seen young multilocular sporangia and parasitic 

 Rhizophydia on the same plant, but in no instance have I found these sporangia 

 to be mature. 



In conclusion, it would appear that the effect of the presence of Rhizo- 

 phydium in Ectocarpus cells is to produce results analogous to those found in 

 animal tissues that have become invaded by Bacterial germs of disease. That 

 there is primarily the same stimulation, which, however, does not advance so far 

 as to induce rapid cell divisions, as happens in the case of Bacteria, is manifested 

 by the fact that the parasite containing cells are usually of a somewhat larger 



* Pringskeim, loc. cit., p. 169, 170. 

 t Goebel, Bot. Zeit, 22nd March 1878. 



