118 W. ARCHER. 



change in the appearance of the contents, which become 

 colourless, the wall shrivels up, and the cell finally appears 

 as a dead sac. 



In Synalissa, Avhich, as seen above, forms a strong point, 

 in the opinion of Milller, against the parasitic theory, Bornet 

 adduces figures tending to show that the relations of the 

 gonidia to the hyphse are not genetic, but due solely to 

 mere subsequent mutual apposition, and this sometimes of 

 quite distinct hypha-branches to cells of the alga manifestly 

 arising from the' subdivision of one and the same gonidium. 

 He avers that he has seen in a fertile example of S. conferta 

 some of the gonidia changed into " spores " (?), as if some of 

 the Glceocapsa cells (herefregarded as forming the gonidial 

 element), uninfluenced by their novel position, had pursued 

 their normal algal course of development. 



Bornet sums up the result of his researches (extending 

 over sixty genera belonging to the various tribes of lichens) 

 in the two following propositions: — 1. Every gonidium of a 

 lichen may be referred to a sjDecies of alga. 2. The relations 

 of the hypha with the gonidia are of such a nature as to exclude 

 all possibility that one of these organs can be produced by 

 the other, and the theory of parasitism is alone able to give 

 a satisfactory explanation of them. 



Sometimes, according to the author, the alteration sub- 

 mitted to by the algse is not very visible. This happens 

 mostly when they are composed of independent cells. When 

 they are filamentous the change is often very marked ; they 

 become distorted and broken up, the cells isolated, and the 

 gelatinous envelopes disappear. Again, in certain cases, the 

 general appearance of the alga is little changed, but it is the 

 individual cells of the alga which become altered. As regards 

 Protococcus and Trentepohlia {Chroolepus) , these are, at first 

 glance, little changed, but the empty cells met with in the 

 deeper parts of the thallus seem to the author to show that 

 they are subject to a real action of the hypha, although this 

 may not manifest itself by any very marked deformations. 

 The cells of the gonidial-algae preserve, though mainly in the 

 peripheral parts, their faculty of multiplication in the ordinary 

 manner, though, owing to the restricted limits in which they 

 are confined, they rarely take their characteristic form. In 

 certain cases the vegetation of the algae appears to be singu- 

 larly stimulated by the hypha (as Glceocapsa and Stigonema, 

 when transformed into Omphalaria, Synalissa, Ephebe, Sec). 

 The gonidia again, in their turn, exert an evident influence 

 on the hypha. On contact with them, it acquires an increase 

 of vitality, manifested by a rapid multiplication of cells, and 



