ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 889 



tissue, or excipulum proper, in Pertusaria ; c, from the hypothecium, 

 in Phlyctis. 



4. From this power of producing shoots must be distinguished the 

 division of the apothecium, by which, in Pertusaria, the isolated por- 

 tions of the apothecium are produced, and in Gyrophora those 

 chamber?, each of which, separated from the others by a circular wall 

 must also be regarded as a thallus-apothecium. 



5. In Pertusaria no paraphyses are formed ; the asci are developed 

 directly in the original tissue. 



6. In Phlyctis agelcea the paraphyses begin to shoot while the 

 asci are dying off, and thus again take part in the formation of the 

 thallus. 



7. The apothecium of Phialopsis, at first entirely angiocarpous, is 

 subsequently rendered gymnocarpous by secondary processes. 



Structure of Crustaceous Lichens.* — J. Steiner has carefully 

 studied the structure of the thallus of crustaceous lichens, especially 

 in the cases of Verrucaria calciseda and Petractis exantliematica. He 

 finds two ways in which the gonidia are formed. The first is an endo- 

 genous mode, by division of the entire protoplasm of the hyphal cells, 

 after it has surrounded itself with a new membrane. The other is a 

 kind of free-cell-formation, several daughter-cells being formed simul- 

 taneously in the protoplasm of the mother-cell. The author also 

 finds that micro-gonidia (of Minks) are formed in the mother-cell 

 by free-cell-formation. He uses chromic acid largely in his 

 preparations. 



Coenogonium and the Schwendenerian Theory.f — The genus 

 Coenogonium, established in 1820 by Ehrenberg, comprises about 

 twenty species which grow in the warm regions of the two hemi- 

 spheres. The filamatous elements of the thallus present a great resem- 

 blance to the filaments of Conferva, and Dr. Karsten and Professor 

 Schwendener recognized in 1862 that around some large coufervoid 

 filaments there exist other filaments much more slender, having a 

 diameter of about 1-2 /a, which appear to be hyaline, and which creep 

 in some measure on the surface of the large green filaments. There 

 is but one single series around the green filaments, and yet this 

 series is interrupted, the slender filaments not touching laterally 

 in a regular manner, but often showing some anastomosis, and there 

 occasionally form, at least in places, a rather close network. Hence 

 there are two constituent elements in the thallus of Coenogonium as in 

 other Lichens, the large green cells still enclosed in their mother-cells, 

 corresponding to the gonidia, and the slender hyaline filaments corre- 

 sponding to the hyphal filaments. 



It is clear, then, writes Dr. J. Miiller, " that according to the 

 celebrated theory of Professor Schwendener, announced in 1867, 

 the large green filaments will represent the nourishing alga, and the 



* Programme k. k. Staats-Obergymnasiums, Klagenfiirt, xxxi. (1881) (2 pis.). 

 See Bot. Centralbl., viii. (1881) p. 228. 



t Arch. Sci. Phys. et Nat., 1881, p. 370. Ann. and Mag. Nat. Hist., viii. 

 (1881) pp. 427-9. Grevillea, x. (1882) pp. 87-9. 



