148 NYLANDEK OH THE ALGO-LICHEN HYPOTHESIS, &C. 



lichens in a gonidic or gonimic respect. Nay, I have pointed out 

 the presence of apothecia in true Chroolepi (constituting the t h alii 

 of Verrucaria melathelia and Artlionia chroolepida), and not a few 

 thalli occur with chroolepoid gonidia of a violet scent (as for the 

 first time I have shown in " Flora," 1870, p. 52). So far, then, 

 are what are called " Algae," according to the turbid hypothesis of 

 Schwendener, and regarded as the " nourishers of the parasites of 

 fungo-lichens," from constituting true algae, that on the contrary 

 it may be affirmed that they have a lichenose nature, whence it 

 follows that these " algae" (or more correctly pseudo-algae) are in 

 a systematic arrangement to be referred rather to the lichens, and 

 that the class of algae hitherto so vaguely limited, should be cir- 

 cumscribed by new and truer limits." Nyl., Obs., Pyr. Or., pp. 

 45-47. The boundary of lichens has also by my aid in this sense 

 been enlarged, for to it I have annexed such genera as Cora, Dicho- 

 nema, Scytonema, Sirosiphon. In " Hedwigia," 1852, p. 3, Cohn, 

 in a paper on Protococcus, already indicates "the existence of zoo- 

 spores, not only in the Algae, but also in the lichens (developing 

 themselves in their gonidia) as a possible thing." The origin of the 

 Schwendenerian hypothesis seems to be as follows : —In Th. Fr. 

 " Stereoc," p. 16, are mentioned, " Cephalodia composed of gelati- 

 nous fibres, intricately congested and blackish." I have shown that 

 the author, led astray by his inexperience, took the common and 

 widely-distributed Sirosiphon saxicola, Naeg., which is to be found 

 on so many different lichens, for the cephalodia of Stereocaulon denu-' 

 datum. Then is devised the Friesian algo4ichen dispute. Sirosiphon, 

 willing or unwilling, is intruded in the cephalodia. The gonimia of 

 cephalodia. become " parasite algae," accordingto the discovery of the 

 writer of Upsala. With respect to these, I have written in " Lich. 

 Lapp. Or." p. 117, "If the various gonimia in cephalodia are to be 

 assumed to be algae, all gonidia must be declared to be such para- 

 sites ;" which immediately afterwards {Schwendener declared to be 

 the case. But more recently Norman (in an article on Moriola), 

 has made known observations somewhat analogous, but much new r er, 

 more wonderful and worthy of attention — observations which so far 

 from sustaining the hypothesis of Schwendener, on the contrary, 

 quite weaken it. 



On the same page of Dr. Weddell's paper already cited, we 

 read — " It has been repeatedly stated that lichens live exclusively, 

 or nearly exclusively, at the expense of the atmosphere ; but it is 

 apparent that the rain-water which periodically impregnates them, 

 and which serves as a vehicle for many diverse substances, whether 

 organic or mineral — substances which a crowd of accidental cir- 

 cumstances brings upon the localities — contributes at least an equal 

 part of their nutrition." Also, p. 6 — " It would be very difficult 

 in many cases to explain without the concurrence of rain-water the 

 presence, so general, of lime in the th alius of crustaceous lichens, 

 which has without doubt penetrated in the condition of soluble 

 carbonate." Whence does the author obtain such an exact know- 



