10 LINDSAY, ON POLYMORPHISM IN LICHENS. 



the physiological relation of the Spermogonia to the Apothecia 

 or perithecia — of the Spermatia to the Sporidia — save the cir- 

 cumstance that no act equivalent to impregnation has yet 

 been actually observed. If my observations and those of 

 Gibelli, as to the discovery of Spermatia and Sporidia in the 

 same conceptacle, should hereafter be confirmed, the fact then 

 proved will furnish a strong argument in favour of the pro- 

 bability of the occurrence of some such action or function as 

 impregnation. Meanwhile, if we assume the physiological 

 relation of Spermogonia to Apothecia, lichens maybe regarded, 

 as they have been described by Bayrhoffer and other specula- 

 tive writers, as Monacious and Dicecious, according as Sper- 

 mogonia occur on the same individuals with the apothecia or 

 not. It is in the latter case especially, — where Spermogonia 

 occur by themselves — that the most expert lichenologist and 

 the most careful student will frequently find it next to im- 

 possible to determine to what species or genus to refer the 

 isolated and secondary organs in question. Fortunately, the 

 general rule is that Lichens are monacious ; and in the cases 

 in which they are diacious, they are more frequently so acci- 

 dentally than normally. 



There are many other forms of polymorphism in the re- 

 productive organs or bodies of Lichens, which are of great 

 interest to the philosophical botanist. Our knowledge 

 thereof consists, however, of fragmentary and isolated ob- 

 servations, casually made in different parts of Europe. They 

 are not more numerous, I believe, simply because Lichen- 

 ology has been hitherto almost exclusively studied by mere 

 systeniatists — by species-makers, who describe phases of 

 plant-life as species, genera, or groups ! Philosophical bio- 

 graphers of Lichens have been very few — physiologists, I 

 mean — who have given themselves the time-consuming, and 

 often fruitless, task of studying all the phases of development 

 of even a single Lichen. Such labour I believe to be of the 

 most recondite character ; and it is, perhaps, not surprising 

 that Lichenologists should always have preferred the in- 

 finitely more easy task of discovering and describing so- 

 called new species, three-fourths, however, whereof will, 

 probably, ultimately be shown by the philosophical Lichen- 

 biographer to be merely /orm5 or conditions of groivth, un- 

 deserving, for the most part, separate nomenclature. 



There is a most puzzling polymorphism in Gonidic segmen- 

 tation in Lichens, and its results under varying external in- 

 fluences, e. ff. temperature and moisture. The Lcprarioid 

 stage of development of Lichens — the fruit of gonidic seg- 

 mentation — has, in the hands of systematists, hitherto been 



