506 BOTANICAL GAZETTE [JUNE 
The third section of the monograph contains a discussion of this symplastic 
or amorphous state, in which it is claimed that all bacteria may live and from 
which new cells may form. The monograph concludes with brief discus- 
sions of ‘‘conjunction” and of methods of study. While L6unis’ discussion 
of pleomorphism is excellent, it must be admitted that the sections dealing 
with reproductive organs and with symplasm are not entirely convincing. 
It is at times difficult to follow his interpretations of the illustrations. At the 
same time, the monograph is very suggestive of lines of work which ought to 
be followed in the study of the life cycles of the lower organisms. Such 
investigations would be well worth while.—J. F. Norton. 
Mycorhiza of forest trees——The conclusions of McDouGaLi”' that “the 
tree is not benefited by association with the fungus, and that the ectotrophic 
mycorhizas are not symbiotic associations, but are instances of the parasitism 
of fungi on the roots of trees,” have caused some doubt of the importance 
ascribed to root fungi by FRANK and other earlier workers. A recent preliminary 
may be quite unimportant for many American trees, they nevertheless assist 
in the nutritive processes of certain species, and may be an absolute necessity 
for some, as recently shown by RAYNER?3 in the case of Calluna vulgaris. 
In the present investigation Metin has found that the mycorhizas of 
Pinus silvestris and Picea Abies cause a limited development of rootlets. 
In the former the dichotomous branching is often modified by the development 
of nodules as large as peas, composed of many densely crowded short branches. 
and one from the Picea. They have been preliminarily called Mycelium 
radicis silvestris and M. radicis abietis. Their systematic position and internal 
relations are for the present left open. They are aerobic organisms growing 
more vigorously in an acid substratum, are exceedingly specialized, and develop 
wly. No fixation of nitrogen takes place in pure cultures of the fungi, 
although there is evidence that the mycorhizas of Pinus silvestris fix the nitrogen 
of the air. Seeds of both these trees germinate without the fungi, and ae 
is no dissemination of the fungi by the seed. The fungi from pure cultu 
infect sterile seedlings through root hairs, and the young plants then ane 
more vigorously. At first the hyphae grow principally in the interior of 
cortical cells, where they form a pseudoparenchyma of the same appearance 
as in the fungus mantle of the completely developed mycorhiza. Later the 
“Hartig tissue” and the fungus mantle are formed.—Geo. D. FULLER. 
* McDovueaLt, W. B., On the mycorhizas of forest trees. Amer. Jour. Bot. 
1251-74. pls. 4. fig. I. 1914. 
22 MELIN, Extras, On the ype : Pinus silvestris L. and Picea Abies Karst. 
A preliminary note. Jour. Ecol, 9:254-257. 19 
23 RAYNER, M. C., Obligate Gime in Callens vulgaris. Ann. Botany 29:97- 
153- 1915. 
