/4 



THALLOPHYTES. 



II. j4lg(B avith Chlorophyll-green Contents. 



Name of Group of Algae. Lichen on which tliey occur as Gonidia. 



(6) Confervaceae . . Coenogonium, Cystocoleus. 



(7) Chroolepideae . . Graphideae, Verrucarieae, Roccella. 



(8) Palmellaceae . . Many fruticose and foliaceous Lichens : 



e. g. Cystococcus humicola on Physcia, Cladonia, Evernia, Usnea, Bryopogon, and 

 Anaptychia^ 

 Pleurococcus, on Endocarpon and various crustaceoiis Lichens. 



Since anatomical and analytical research has led to this view of the nature of 

 Lichens, the next step must be to complete synthetically the proof of its correctness by 

 sowing the spores of the Lichen-fungi on or near those Algas which serve as their gonidia, 

 and to induce their germinating filaments and the hyphae which proceed from them to 

 invest the Algae ^. If in this manner a true Lichen-thallus is obtained, each fresh case in 

 which this is successful would furnish a new proof of the correctness of Schwendener's 

 theory. This synthetical method has already been adopted by Reess with the greatest 

 success ; for he has succeeded in growing in this manner the Lichen-thallus of Collema 

 glaucescens both from germinating spores of the same species and from Nostoc lichenoides^. 



SUPPLEMENT. 

 MYXOMYCETES^ 



Under this head is included a numerous group of organisms which in many 

 respects differ widely from all other vegetable structures, but, in the mode of 

 formation of their spores, stand nearest to Fungi, on which account we may treat 

 them as a supplement to that class. The .]\Iyxomycetes are remarkable in no 

 ordinary degree from the fact that during the period of their vegetation and assimi- 

 lation of food they do not form cells or tissues. The protoplasm, which in all 

 other plants is also the general motive power of the phenomena of life, remains 

 in them during the whole of this period perfectly free, collects into considerable 

 masses, and assumes various shapes from the internal force residing in it, with- 

 out becoming divided into small portions which surround themselves with cell- 

 walls (or become cells). It is only when the protoplasm passes into a condition 

 of rest in consequence of being surrounded by unfavourable conditions, or when 

 it concludes its period of vegetation by the formation of the reproductive organs — 

 its internal and external movements ceasing at the same time — that it breaks up 

 into small portions which surround themselves with cell-walls, and which even then 

 never form a tissue in the proper sense of the term. 



1 See Schwendener in Nageli's Beitrage, &c. 1868. Heft VL pp. no, 11 1. 



2 [See Bomet, Annales des Sci. Nat. 5th series, 1873, vol. XVII.— Treub, Bot. Zeitg. 1873, 

 pp. 721-727.] 



3 Monatsberichte der konigl. Akad. der Wiss. zu Berlin. Oct. 1871. Compare further, Schwen- 

 dener, Flora, 1872, nos. n and 12. [Quart. Journ. Micr. Sc. 1873, p. 235 ; compare Archer, Quart. 

 Journ. Micr. Sc. 1872, p. 367.] 



* De Bary, Die Mycetozoen, in the Zeitschrift fiir wiss. Zool. vol. X. 1859 ; separate 2nd edition, 

 Leipzig, 1863; (this work is the leading authority for the whole group). [Ann. Nat. Hist, i860, 

 vol. V. p. 233.]— Cienkowski in Jahrb. fur wiss. Bot. vol. III. pp. 325, 400.— Oscar Brefeld, Ueber 

 Dictyostelion mucoroides, Abhandlungen der Senkenhergischen Gesellschaft, vol. VII. Frankfort 1869, 



