THE LTCITEX SY^rilTOSTS 20-' 



sortia ])()th grow on the bark of trees, or tliose of PcHigrra aiul 

 Clcahiiia botli among g]-as.s, and vet be so widely divergent in their 

 new factors? The only factor tliat appears to be connnon to all 

 is the differentiation of a close weft of ])seud()-parenchynia as a screen 

 over the tract of dissociated photosynthetic algic ; and even this is not 

 always done in the same way [cf. Ephche and the tine thalloid sluxjts 

 of JioceUa fu ci forming wholly wanting also in many genera (^Crocipiia) 

 or more clearly simulating an acpieons epidermis]. 



One begins to donbt the symbiont partnership as having anything 

 to do with the matter, though one may be })ut ott' with the idea that 

 the range of variability in such a ' nascent,' and hence ' labile ' 

 organism (Keinke, 1.S95, p. 69) initiating new departures, may be 

 excessive; just as Sachs {loc. c/'f.) put it all down to the chlorophyll. 

 Perhaps the somatic organization is not so very new after all : even 

 among Ascomycetes of holosai)r()phytic habit very striking growth- 

 forms may still be retained ; the case of Xylaria polymorph a with 

 bilateral, erected, stromata, branched more or less irregularly or 

 dichotomously at the distal end, and bearing indefinite ' cystocarpic ' 

 perithecia in its cortex, presents suspiciously comparable form-factors. 

 And one's doubts are confirmed when a little consideration shows 

 tliai not one of these factors is anything new after all. Thev are, 

 in fact, only a repetition of the commonest of commonplace factors of 

 the somatic organization of algte, as seen in modern seaweeds, in 

 M'hich centric cable-stranded axes, hollow, or with skeletal axial 

 strand— or, again, dorsiventral shoot-systems attached by rhizoidal 

 processes, indefinite in ramification, or proliferating subdichotomonsly, 

 with differentiation of a dense ' cortical ' layer, more or less ])rotective 

 against intrusion — are the prevailing methods of somatic elaboration. 

 Again, these and no other, in similar filamentous wefted growth- 

 forms (' cable-strand types of aggregation '), are the working mechanism 

 of Green (Siphonea^), Ked (Floridea?), and Brown (Phii^osporeie) 

 algal phyla of the sea. For example, the building of massive radially 

 symmetrical axes, with preferential apical growth, and capacity for 

 throwing out laterals of similar organization, repeating the construc- 

 tion, is a mechanism involving numerous controlling form-factors, 

 each of which can be only established in marine organism as response 

 to changes in a certain environment by rigorous natural selection. So 

 far as known, such factors of organization can be only evolved in the 

 conditions of marine phytobenthon, consequent on the attachment 

 of encysted plankton-flagellates to a substratum within the range of 

 light-penetration. It is to the sea that one must look foi'^ the 

 analogue of any specialized lichen-thallus ; and a glance over the 

 pages of any set of illustrations of lichen-types at once discloses their 

 essential morphological identity with forms of autotrophic marine 

 organism, more jxirticularly in the manner of Floridean types of 

 somata, as the small, clustered, or encrusting growths of reef-pool 

 foi-mations. That is to say, since a seaweed can only arise in the sea, 

 as the response of autotrophic life to special benthic conditions in 

 sea-water, the presumj^tion is that any plant presenting similar 

 somatic characteristics must have arisen in the sea also. 



The resemblance of such plants, both in general size and shoot- 



