1922] Ames,—Notes on New England Orchids,—II 43 
out the early stages of development in the protocorm. As the proto- 
corm gives rise to the rhizome, and leaves and roots begin to develop, 
the fungus passes into the cortical cells of the roots. From my obser- 
vations it does not again invade the tissues of the rhizome. In adult 
plants invasion of the roots takes place directly from the humus. All 
the evidence shows that the association is a close one and that both 
fungus and orchid derive some benefit from it. The capacity of both 
organisms to thrive, is, it would seem, a sufficient proof that orchid- 
fungus symbiosis is a well balanced condition. It is true that some 
of the cells occupied by the fungus frequently exhibit large lobed 
nuclei, or that a cell may be occupied by two or more nuclei which are 
formed directly by fragmentation. This may be taken to indicate a 
pathological condition. Nevertheless, the fungus is digested in the 
cells farthest removed from the growing point of the protocorm, in 
tissues that are soon sloughed off as the protocorm elongates (pl. 
136, figs. 5 & 6). 
Reimheimer! would have us believe that the orchid-fungus associa- 
tion is no longer advantageous, although it is possible that in the past 
and under special conditions, the fungi have been more useful to the 
orchids than frequently they are now. If the orchid is capable of 
nonsymbiotie germination as Knudson and Bernard have demon- 
strated by laboratory experiments, and the ever present fungus is 
assumed to be an unnecessary evil in a forced association, sometimes 
even causing the death of the embryo, how are we to reconcile this 
assumption with the evidence that may be turned to prove that the 
orchid family has been eminently successful? The family as at present 
known is one of the largest phanerogamic groups, numbering some 
five hundred and fifty genera and fifteen thousand species. In the 
diversity of floral structure, in the adaptation of the perianth and gy- 
nostemium to pollination by insects, and in the extraordinary modi- 
fication of the vegetative parts to meet the exigencies of terrestrial 
and epiphytal distribution, the orchids are unsurpassed by any other 
plant family. Furthermore the Orchidaceae constitute the predom- 
inant group as to number of species in some of the richest floral 
regions of the globe. In Borneo? and the Philippines, for example, 
4 Symbiosis, A Socio-physiological Study of Evolution (1920). 
5 Merrill in Journ. Str. Br. Roy As. Soc. Special No. (1921): Orchidaceae 86 gen- 
era, 702 species; Rubiaceae 64 genera, 333 species; Euphorbiaceae 57 genera, 195 
species; Leguminosae 59 genera, 174 species. 
