ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
779 
Pachytheca.* * * § — Mr. C. A. Barber has carefully studied numerous 
specimens of this fossil from the Old Red Sandstone and Silurian forma- 
tions, and concludes that it is a spherical alga consisting of a mass of 
cellular filaments. The cells of these filaments appear to resemble in 
general shape those of a living Cladophora. 
Dr. W. T. Thiselton-Dyer f confirms Mr. Barber’s statement of an 
organic connection between the cortical cells and those of the peripheral 
tissue. 
Fungi. 
Mycorhiza.J — M. P. Vuillemin adopts Frank’s view with regard to 
the nature of mycorhiza. He proposes the classification of the various 
kinds into Ascorhizae and Basidiorhizae, and the latter again into 
Hymenorhizae and Gasterorhizae. For the corresponding structure in 
Corallorhiza and Epipogium he suggests the term mycorhizome. 
Endotrophic Mycorhiza.§ — Summing up the present state of our 
knowledge with regard to the various instances of endotrophic mycorhiza, 
Herr B. Frank regards them as fungus-consuming plants, comparable to 
other carnivorous plants, which have the power of attracting the fungus 
into their protoplasm, and finally digesting it. The organs in which this 
digestion takes place are not true roots, but new formations of a peculiar 
morphological character, for which he proposes the term mycodomatia or 
fungus-chambers. The known examples of endotrophic mycorhiza may 
be classed under the following four heads : — 
(1) Endotrophic Mycorhiza of the Orchideae. The fungus is here, 
from the first moment of its development until the close of its life, 
completely inclosed in the active protoplasm of the root-cell. The 
fungus-hyphae gradually lose their albuminous contents, and give them 
up entirely to the host, losing, at the same time, their power of indepen- 
dent growth. 
(2) Endotrophic Mycorhiza of the Ericaceae. The phenomena are 
here very similar to those which occur in the Orchideae. 
(3) Symbiosis of the Leguminosae. The Schizomycete is here taken 
up from the soil into the cells of the root, and there digested in the 
root-tubers formed for the purpose. But when the bacteroid tissue has 
been absorbed, some germs still remain which return to the soil on the 
decay of the tuber. 
(4) Symbiosis of the Alder. The process shows a complete analogy 
with those of the Leguminosae. The formation of sporanges by Frankia 
subtilis, described by Brunchorst, appears to rest on erroneous observation. 
The ectotrophic mycorhiza of the Cupuliferae and Coniferae does 
not come under either of the above headings. 
Disarticulation of Conids in the Peronosporege.||— According to 
M. L. Mangin, the septum which separates the conid from the basid or 
* Arm. of Bot., iii. (1890) pp. 141-8 (1 pi.) ; v. (1891) pp 145-62 (1 pi.) 
t Op. cit., v. (1891) pp. 223-5. 
j Rev. Gen. Sci. pures et appliquees, i. (1890) pp. 326-35. See Bot. Centralbl , 
1891, Beih., p. 192. 
§ Ber. Deutsch. Bot. Gesell., ix. (1891) pp. 244-53. Cf. this Journal, ante, p. 504. 
|| Bull. Soc. Bot. France, xxxviii. (1891) pp. 176-84, 232-6 (1 pi.). Cf. this 
Journal, ante , p. 381. 
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