198 THE ORCHID REVIEW. JULY, 1922- 
Pfeffer, or a modification thereof, differing principally in having an 
ammonium salt in place of anitrate. (The cultures were all grown under 
aseptic conditions and the seeds were sterilized with calcium hypochlorite). 
In preliminary experiments it was shown by planting seeds on various 
organic extracts (peat, carrot, etc.), that ‘‘ germination of seeds of Cattleya 
and Lelia is possible without the aid of the fungus, provided soluble 
organic substances are present, particularly sugars.” Growth, however, 
appears slower than under ordinary cultural conditions, and Knudson 
suggests that in the latter case, the fungus may play a part, but that it is 
also possitle for certain organic products of decomposition of the 
substratum, to be involved in germination. Knudson and Lindstrom 
showed in their experiments with albino corn, that a full nutrient medium 
plus sugar is not capable of sustaining continued growth: plants kept 
either in the light or in the dark and supplied with one of several sugars all 
died aftera month ortwo. These experiments, together with the well-known 
results obtained by the late Professor Bottomley, on the beneficial effect of 
auximones, and those of several recent authors on the influence of vegetable 
extracts on the growth of fungi, suggested that more rapid germination, 
and more vigorous plants, could be obtained if a vegetable extract were added 
to the nutrient medium. This was put to the test, the extracts used being 
potato, wheat, beet and yeast, all of which apparently had a stimulating 
effect on growth. These results are comparable with those obtained in 
experiments on animal nutrition, where accessory food factors (vitamines), 
are found to havea similar beneficial effect. The results of five series of 
experiments are given, the details of which cannot be gone into here; they 
deal further with the influence of concentration of sugar, the influence of 
micro-organisms (i.e., other than root fungi) and transplanting experiments. 
It will be seen from the above that no really new facts have been added 
to our knowledge ; the value of the work lies in the precising of certain 
factors, though many of these call for still further analysis. The theoretical 
conclusions reached are, however, quite different from those which have 
previously been generally accepted. Bernard, convinced of the necessity 
of the fungus for normal germination, attempted to replace its action by 
chemical stimulation, and succeeded in the case of Cattleya and Lelia-gener@ 
which, it may be added, cause little trouble to the grower. (These results 
were confirmed by Mr. Charlesworth and the present writer, though 
attempts to extend the method to Odontoglossum and its allies have so far 
failed). Knudson, on the contrary, approaching the question from a study 
of these genera and not having experimented with the fungi, is biassed 
against accepting the fungus theory as necessarily the correct one. He 
lays stress on certain statements of Bernard. ‘‘ Granting for the present 
that a symbiotic relationship exists between the fungus and the embryo, it 
