236 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



cell-division. As to additional details of the processes of 

 nuclear and cell-division, the small size of the objects 

 makes study very difficult, and because this has no direct 

 bearing on the main problem discussed here, I leave the 

 matter as it now stands. 



VIII. Summary. 



The results of this examination of a few forms, though 

 admittedly of too few and too like forms to justify anything 

 more definite than an opinion regarding lichens in general, 

 may still be of value as a contribution to the discussion of 

 the relation of fungus and alga in lichens and of the 

 so-called autonomy of lichens. These results may be 

 briefly stated as follows: — 



I. Both cultures and thin microtome sections demonstrate 



I — that hyphse and gonidia are in the most intimate 

 contact; 



2 — that the hyphae develop branches which may merely 

 clasp the gonidial cells or may, as definite haus- 

 toria, penetrate them; 



3 — that such clasping or penetration stimulates the 

 gonidia to internal cell-divisions in the effort to 

 form individual cells free from hyphal investment; 



4 — that the haustoria consume the protoplasmic con- 

 tents of the gonidial cells which they have entered, 

 leaving only the empty cell-wall. 



II. I — Since the fungus, being devoid of chlorophyll, must 

 obtain already elaborated non-nitrogenous food; 

 2 — since the only constituent of the lichen capable of 



elaborating non-nitrogenous food is the gonidia; 

 3 — and since lichens ordinarily grow where they could 

 obtain little or no non-nitrogenous food from the 

 substratum even if they were dependent upon it 

 for other than mechanical support and mineral salts, 

 — it is obvious that the fungus is fed by the alga; 

 the hyphae, by the gonidia. 



