280 BEV. J. M. CEOMBIE ON THE ALGO-L1CHEN HYPOTHESIS. 



well seen in the isidia) in the gelatinous thalline substance before 

 the medullary hyphse, amongst which they are seen lying either 

 scattered, or usually conjoined, or variously conglomerated, and 

 constituting, as also each isidium does, what Nylander has termed 

 a " syngonimium." The lichenohyphse of the medulla, when 

 they are present (for here also, as in the Lichenacei, the medulla 

 is sometimes entirely cellulose), most probably originate from the 

 cortical stratum, which is more or less evolute, though this point 

 requires further investigation. But however this may be, their 

 relation in every instance to the gonimia is in no way one of 

 copulation or parasitism, but simply and solely, as already stated, 

 of adhesion (where such exists) by means of the licheniu which 

 permeates the thallus. 



In the Ephebacei again, the whole thallus, i. e. each single fila- 

 ment from the base to the apex, or each siugle fruticule more or 

 less branched from the base to the apices, constitutes also a syn- 

 gonimium. The gonimia here, which are tunicated, or involved 

 in a gelatinous membrane, originate within the cellules, and after 

 the formation of the cellules, in the manner so fully described by 

 Nylander when treating of Nematonostoc {vide Bull. Soc. Bot. 

 1873, pp. 263, 264). Since this evidently elucidates also the 

 evolution of the gonimia in the Collemacei, his observations may 

 here with propriety be transcribed, subversive as they are alike 

 of Schwendenerism and Minksianism. " In a physiological 

 respect," he says, " it is to be noticed that this Nematonostoc (as is 

 usual in analogous thalli) is propagated by gemmules, or minute 

 isidiomorphous globules. These gemmules are at first globulose, 

 simple, agonimic cellules, which in growing become oblong and 

 are divided by a septum : afterwards by the addition of a cruciate 

 septum they are seen to be quadrilocular, and gradually pluri- 

 cellulose. But at the same time, in these gemmules, while still 

 in a young state, are pioduced the gonimia, at first a single 

 gonimium in each loculus, and later two and more (through the 

 division by constriction of the first gonimium), so that monili- 

 form gonimia are produced, and in maturity the internal cellulose 

 texture disappears. Thus from the very beginning the gonimia 

 are produced within the cellules, and after the formation of the 

 involving cellules." Such briefly stated is unquestionably the 

 origin and the subsequent evolution of the gonimia alike in 

 the Ephebacei and the Collemacei, as demonstrated on a microsco- 

 pical examination of the isidia, or so-called Nostocine conditions 



