105 
fern species, the interpretation of occasional collections, inter- 
mediate between recognized species, as hybrids, came more and 
more into acceptance in the United States and in Europe. The 
ereatest number of these putative hybrids were found in a section 
of the genus, Dryopteris, but ascription of hybrid identity has 
also been made in Asplenium, Camptosorus, and other gencra, 
including, most recently, Osmunda. 
pete 
Latterly a number of developments have occurred which have 
raised interesting questions both regarding these presumptive 
hybrids and about the range of variation and differentiation 
among the fern species involved. Increased collections over 
wider ranges have indicated that the limits formerly assigned 
to some of our species must cither be extended, or that sub- 
divisions of these species will have to be made. For some of 
these possible subdivisions differences of opinion have arisen as 
to whether certain types are to be interpreted as hybrids or as 
distinct species or in lower categories. Furthermore, some of the 
best attested of the hybrids have been found to manifest spore 
fertility and to reproduce themselves true to spores, a state not 
noted in connection with any of the morc extensive earlier studies. 
Altogether, these ferns offer a series of challenging problems 
not only in identification and classification, but also for an 
experimental attack on the basic factors involved. At present, 
the outdoor culture under approximately uniform conditions of 
recent collections is being carried on under slat shade in the 
experimental grounds. Field trips and correspondence have 
added to the collections including a few plants from outside our 
local range. 
ECONOMIC PLANTS 
By RatepHu H. CHENEY 
The subjects of investigation, during 1941, have been as 
follows: 
