88 Proceedings of the Royal Irish Academy. 



those who hold strch a view must take refuge in the assumptioii of the 

 formation of the first gonidium in the germination of the spore — a 

 process which has not yet been observed in any Kchen, and, d priori, 

 never will be. 



But it must be pointed out that, according to Schwendener and 

 others, Scytonematous and Sirosiphonaceous algse ai-e claimed as foiTa- 

 ing"gonidia" under two distinct circumstances or conditions: they 

 are, according to their researches, to be found in certain lichens, either 

 as mere accidentally detached portions of filaments wholly surrounded 

 and involved by the hyphae, and caught up bodily in the substance of 

 the lichen-thallus in a completely disorderly manner, or they exist as 

 perfect plants of their type as algae, the alga-thallus quite unaltered in 

 outward configuration, but permeated along the length of the filaments 

 by the hyphse, which run between the rows of green cells. When the 

 algae, as is assumed, are in the former way compelled to become the 

 " gonidia-foimers," it is the hyphae (not the algas) which must be held 

 to control the configuration of the thallus and determine the character- 

 istic build-up of the " lichen ; " when the algae serve in the latter way 

 as gonidia to the intruding hyphae, the foi-mer (not the hyphae) retain 

 their proper " specific " exterior, the build-up of the (algal) thallus is 

 not externally altered, and it is only a microscopical examination which 

 would reveal anything unusual or offer any " liehenous " indication. 

 It is as regards this latter gonidial condition that Schwendener's argu- 

 ments, as to the impossibility of the genetic relationship of the hyphae 

 and the young apical gonidia, by reason of the latter being formed 

 prior to the arrival at the apex of the hyphal filaments, are directed, 

 and to this condition it is that the notes here brought forward apply. 



One of the most common of the Scytonemacece is the Scytonema myo- 

 chrous, forming silky cushion-like tufts on wet rocks, when dry, of 

 mouse colour, when wet, more of an olive hue ; it seems to love best a 

 pretty constant trickle, and if the force of the little ciu'rent be some- 

 Avhat strong, the mass may form a rather long drawn-out pad, stretch- 

 ing down the inclination of the surface over which the little flow de- 

 scends. Very often in my searchings I gathered little portions from 

 various sites, sometimes very wet, sometimes, indeed, dried up by 

 drought, and once only was I so fortunate as to find examples showing 

 apothecia. I regret I have mislaid my rough drawing of the apothe- 

 cium itself, but fig. 1 is a sketch of the spores within an ascus. The 

 general appearance of the apothecium, however, is like that of Sirosi- 

 phon. The asci were accompanied by linear paraphyses ; the spores were 

 four in an ascus, nearly coloiu'less, broadly elliptic, simple, with two 

 bright corpuscles, each with a minute dot in its centre immersed 

 therein, one towards either end. Length of the spore, — ", breadth, 



' O 1 J 35D0 ' ' 



.4'(%«-1^2). 



Another Scytonema, whose precise identity seems difficult to deter- 

 mine, also presented apothecia. This too I found on only one occa- 

 sion ; the contents usually formed a thin, somewhat irregular, central 

 string up the middle of a some^vliat thick striated sheath, except near 



