OBSERVATIONS ON COLLKMA. 23 



course, on all hands it is agreed that Lichens and Fungi, save the 

 gonidia, have between them no absolute line of demarcation. 



Seemingly at first more impressed with the applicability of the 

 theory to the Collemacese, though he no doubt afterwards accepts 



its complete tenabilit j as regards the whole class of the " Lichens," 

 Reess conceived the idea of " sowing" the spores of Collema upon 

 the substance of Nostoc, and a description of the experiment and 

 its results forms the subject of his memoir previously alluded to.* 

 He states, indeed, that the spores of Collema ran be readily enough 

 made to germinate upon any moist substratum, such as a glass-plate, 

 stones, and so on, and will slowly produce even a branched and 

 sparingly jointed growth, but this goes on only so long as the reserve- 

 stuff is supplied by the spore, but when this is exhausted the liypha- 

 mass thus produced, though it may survive even weeks, will then 

 slowly die off. But when he brings a spore or the young hypha 

 upon the Nostoc, it at once becomes further developed, sending more 

 or less copiously through its surface many branches, and penetrat- 

 ing within. Soon, however, they cease to increase in length, be- 

 come swollen at the points and at other places, and become attached 

 by these swellings upon the Nostoc. Thereupon thinner processes 

 become sent further into the gelatinous mass of the Nostoc, from the 

 swellings ; these become branched, and, tortuously surrounding the 

 chains of gonidia, form, in fact, the " Collema-mycelium," and the 

 complete transformation or conversion of the " Nostoc" into the 

 Collema is brought about by the hypha producing a peripheral 

 stratum of fibres, from which break forth, through the " Nostoc - 

 jelly," the first root hairs. Such an artificially -produced " Collema" 

 the author had not been able to rear up as far as the production 

 of fructification (apothecia), but he doubts not the tenability of the 

 assumption that every Collema in free nature is a " Nostoc" thus 

 made the nidus for the development of the spores, evolved of course 

 from a preceding " Nostoc " so naturally inoculated (as one might 

 say), i.e., in other words, a preceding compound organisation which is 

 known as " Collema." Such is, as brief as possible, the result of 

 Reess's experiences, and the views he holds ; it would far exceed 

 the limits available in these pages to go more closely into the 

 arguments and statements of Reess and Schwendener — those of 

 the latter applied to the Lichens at large, not the Collemaceaj only 

 — but it may not be wholly without use to have directed attention 

 to their remarkable memoirs. 



Basing his opinion, as it would seem, at least mainly, upon the 

 result of the experiments of Professor Reess alluded to, Professor 

 Cohnf would exclude the Collemacere from the Lichens, which 

 ^without these), as a Class, he would retain, remarking that "he 



* Prof. Eeess— "Ueber die Entstehung der Flechte Collema glaucescens, 

 Hoffm. durch Aussaat der Sporen derselben auf Nostoc lichenoides, Vauch." in 

 " Monatsb. der k. Akad. der Wissensch. zu Berlin," Oct. 1871, p. 523. 



f Prof. Dr. F. Cohn — " Conspectus Familiarum cryptogam; i rum secundum 

 method um naturaltm dispositarum," in " Hedwigia," No. 2, 1872, p. 17. 



