CURRENT LITERATURE 
BOOK REVIEWS 
The root-fungi of orchids 
Burcerr' has brought together the extended results of his own research 
and those of other students upon the root-fungi of orchids. The volume con- 
tains a comprehensive citation of literature, several tables summarizing results 
of experiments, and discussions of the theory of the mycorhiza question. By 
way of introduction, BuRcErFF defines his use of the word symbiosis as that 
relation of two symbionts in which one aids the other in any way, if only to 
make existence possible under conditions otherwise impossible. After union, 
the two organisms form a new organism, a unit, which takes up the struggle 
for existence under new conditions, each being a body member. Such is claimed 
to be the condition of the orchids and their root-fungi. ‘The two sections of 
the work are as follows: 
1. The study of the fungus independent of the plant—On a culture medium 
of agar and rain water with a slight trace of starch, 29 root-fungi, aseptically 
obtained from native and tropical orchids, were grown (holosaprophytic ones 
were unsuccessful). Such species of Orcheomyces, as the author chooses to call 
the fungi for convenience, are described in detail as to their structure and 
behavior in the culture. For the first time a study of their enzymes has been 
made, and the endophytes were grouped accordingly on the basis of their 
biological relations to the orchids. In general they have thin-walled, regularly 
septate mycelia; the hyphae are sharply differentiated into Langhyphen that 
branch little and show unlimited growth in one direction, and Kurzhyphen that 
are of smaller caliber and arise at regular intervals and whose cells under 
Chains of hyaline or slightly colored spores may unite into loose clusters or 
closer sclerotia-like groups. All fungi fuse or anastomose in some manner. 
e hyphal cells contain two to ten nuclei, but the spores contain only two 
nuclei. Spiral knots initiated in cultures by the surface tension of a drop of 
water at the tip of the hypha are comparable to those in the root cells developed 
in response to the pressure of the resisting plasma membrane to the penetration 
of the hypha. No sexual reproduction was observed. 
« Burcerr, Hans, Die Wurzelpilze der Orchideen; ihre Kultur und ihr Leben 1" 
der Pflanze. 8vo. pp. 207. pls. 3. figs. 38. Jena: Gustav Fischer. 1909- d 
, Zur Biologie der Orchideen Mycorhiza. pp. 66. Inaug. Diss. Jen: 
Gustav Fischer. 1909. : 
386 
