282 REV. J. M. CROMBIE ON THE ALGO-LICHEN HYPOTHESIS. 



mittent manner of life, and especially in their extreme longevity 

 {vide Crombie, Art. " Lichens " in Encyclopaedia Britannica, 

 1882, p. 558) *. Lichens therefore are Lichens and nothing 

 else — neither Fungi nor Algae, nor any intermixture of these ; 

 but everywhere and constantly preserving their own distinct type, 

 and distinguished by many important characters peculiar to them- 

 selves. Such of these as have a more direct bearing upon the 

 solution of the problem before us have been more or less fully 

 noticed in the preceding observations. From these it is suffici- 

 ently evident that Schwendenerism, whether viewed anatomically 

 or biologically, analytically or synthetically, is, instead of being 

 true science, only the " Bomance of Lichenology," as I have 

 elsewhere termed it {vide Pop. Sc. Eev. 1874, p. 276). And thus 

 also the origin of the gonidia in, and their relation to, the rest of 

 the lichen-thallus belong to the very rudiments of Morphological 

 Botany, and constitute the ABC of Lichenology. 



DESCRIPTION OF THE PLATES. 



Plate VIII. 



Fig. 1. Hypothalline state of Cladonia coccifera, magnified, showing the first 



cortical glomerules developed upon the hypothallus, in the cellules of 



which the gonidia originate. After Tulasne. 

 Fig. 2. Similar hypothalline condition of Lecanora gibbosa, magnified. 2a. 



Gonidia as seen enclosed in the cellules of the pseudo-parenchyma, 



magnified about 270 diameters. 

 Fig. 3. Similar hypothalline state of Lecidea alboatra, with dendritically 



arranged filaments and the first minute cortical glomerules, nat. size. 



3a. A portion magnified. 



Plate IX. 



Fig. 4. Lecidea geographica, hypothalline condition, portion, of natural size, a» 

 shown growing on a small piece of quartz rock. 4a. A portion of the 

 same enlarged about four times its nat. size. 



Fig. 5. Thin section of the cellulose cortical stratum and of the medullary 

 hyphaa of Physcia pulverulenta, showing the gonidia originating 

 within the cellules, X 300. 



Fig. 6. Vertical section of thallus of Umbilicaria pusfulata, magnified about 

 250 diameters, showing the genesis of the gonidia within the cellules 

 of the lower portion of the minutely cellulose corticali-gonidial 

 stratum, from which it is evident that they are not in any way pro- 

 duced from the medullary hyphrc (cfr. Nylander in 'Flora,' 1875, 

 p. 303). 



This longevity is to be measured in many cases, not merely by centuries, 

 but apparently by millenniums. 



