THE LICHEN AS TRANSMIGRANT 9 



While the Floridean types still in the sea show the unilocular 

 sporangium reduced to an output of 4 tetraspores — as the minimum 

 number following an act of meiosis, and borne on a free-living 

 individual, — the Ascomycetes, transmigrant to the land, still retain 

 what may be fairly regarded as an older condition of 8 ascospores, 

 beyond the meiotic division ; and the latter is borne on a parasitic sporo- 

 phyte-phase. There is no indication that the limiting number 4, so 

 constant among Florideae, when once established, should be increased 

 to 8 with equal constancy : the claims of subaerial wastage, for 

 example, may augment the output of asci, but are not likely to 

 necessarily affect the established mechanism of spore-production. 



While the algal precursors of the Lichen Fungi thus afford a 

 glimpse of an older and now wholly lost race of marine algae, as well 

 as expressing an older range of the Ascomycete type behind the 

 decadent saprophytic forms — and even suggestions of a wider algal 

 phylum beyond the horizon of the Floridese, — it becomes of interest 

 to follow the course of what would probably have happened to such a 

 race in passing through the vicissitudes of the transmigration epoch, 

 to attain firstly a holosaprophytic habit, and subsequently a recovery 

 of autotrophy in virtue of the helotism of intrusive algse, which has 

 undoubtedly proved curiously successful under certain inferior con- 

 ditions of subaerial environment, in which the plants have no modern 

 competitors. In this respect special interest attaches to the condition 

 described as involving ' intrusive organism ' in the older phase of 

 the sea. 



Starting from the lofty standpoint of the higher animal, one is 

 apt to ignore the fact that every such individual organism may be 

 preferably regarded as a special formation in the ecological sense, 

 quite as much as an individual entity. Even in health we each carry 

 an elaborate flora and fauna of our own. In the sea, conditions of 

 life are even more complex, owing to the difficulty of finding suitable 

 unoccupied substratum for the attachment of benthic organism as 

 anchored hormon. In fact, the inception of free-swimming nekton 

 at any point of the animal-series, may be largely regarded as one 

 form of necessary response to this very restriction of available area in 

 such stations. The same applies to the vast amount of epiphytic, 

 epizoic, endophytic, and actively intrusive organism which charac- 

 terizes the lower forms of plant-life in the sea. Germinating spores, 

 in absence of clean rock, must germinate, it at all, on other organism ; 

 and more massive perennial growth-forms may commonly become 

 wholly clothed and buried in a forest of epiphytes to the limit of 

 their hapteron -capacity 1 . Where the organism is of simple plasmatic 

 nature, or is only invested by thin mucilaginous wall-substance, there 

 is nothing to prevent intrusion by such spores — more particularly if 

 possessed of flagellated and englenoid activity — and the consequent 

 establishment of one organism within another ; taking the chances 



1 Cf. Tide-pool algse smothered in Diatoms: Tendo (1914), Econ. Proc. Roy. 

 Dub. Soc. p. 105, on the commercial culture of Laminaria in Japan, by putting 

 clean rock in the sea at sporing-periods : Borgesen (1908) Botany of the Faeroes, 

 p. 758 ; for list of 25 epiphytes on stems of Laminaria Cloustoni (hyperborea), 

 with zonation, p. 757. 



