388 BOTANICAL GAZETTE [NOVEMBER 
BurGErFF obtained its development, in 0,33 per cent cane sugar with mineral 
salts on agar, in the dark, to the differentiation of papillae, and it lived ten 
months. Further development either in light or dark required the fungus. ° 
While in the light the orchid developed normally, in the dark it elongated and 
resembled the Epidendrum which grew in the weaker concentration of salts. 
BurGEFF concludes that physiologi cally the behavior of the fungus is alike 
in the germination of the epiphyte and the terrestrial orchid, and that the 
appearance of chlorophyll in the epiphyte is an adaptation to its life in the 
light. 
Seedlings with the fungus in absence of CO, in the dark grew, but developed 
no root, while in the light the growth was normal. Experiments on the physi- 
ology of nutrition, where fungus and seedling were grown together, showed the 
best N sources to be ammonium chlorid and nitrate. Although asparagin was 
favorable for the fungus in free culture, the plant could not grow in it. In 
N-free media there was no development. Lactic acid (2 per cent) in minera! 
salt agar culture caused both plant and fungus to grow well. Laelio-Cattleya 
was found to harbor some fungi (17 tested) unable to stimulate its germination: 
BurceErF devotes 50 pages to the histological processes in the ‘growing 
plants. These detail the places of entrance, position of the fungi, peculiar 
features in the plant cell (spores and clumps, K/umpenbildung), the emission 
of hyphae to the substratum, etc. Most of the fungi have mycelial connections 
with the outside substratum, therefore anatomically there is nothing to prevent - 
ascribing to such hyphae the function of conduction of soluble materials. The 
author explains the unwettability of the seeds as due to the Luftbldschen in the 
netted testa itself, and to the air between the testa and embryo (comparable 
to the condition in the lycopod spores). Such unwettability hinders the pas- 
sage of spores through the soil, contrary to the theory of Kocu and LisTNER, 
but is of advantage in preventing the clinging together of seeds in the capsule, 
therefore an adaptation to their dissemination by wind. Also because the seeds 
are chemically attracted to the fungi, the unwettability is an adaptation in 
terrestrial orchids against too rapid exhaustion of this substance. 
BuRGEFF agrees with BERNARD in the probable steps of development of 
the symbiosis by way of parasitism, but would speak of the association not aS 
a “maladie bienfaisante,” but as of “einem gliicklichen Zusammentreffen 
verschiedener Umstinde.” He bases this remark on the following facts: the 
fungus is harmless, its enzymatic qualities separating it from comparison with 
parasites with toxic qualities; it is able to kill an unadapted fungus whose 
penetration it nevertheless allows; its fitness for infection is seen in the 
Durchlasszellen of the embryo. A mutualistic symbiosis demanded by the 
definition is found in this association, for the orchid has to thank the fungus for 
its existence, and the fungus is grateful to the orchid for the materials difficult 
to obtain from the soil which enable it to form spores. As to the materials 
of exchange between the components, the question is left unanswered; but the 
idea of conduction of mineral salts is favored, because of the results of the 
