The importance of hybridization in speciation is emphasized by listing most of the known intergeneric hybrids in flowering plants and including a figure (23,675) of all the known hybrids including interspecife ones. No claims are made that the list is complete or absolutely accurate. Some of the strong points regarding hybridization as a process are given. In addition, it is pointed out that hybrids, throughout the range, show both dominance and intermediacy, some possess normal meiosis and many are highly or partially fertile.

No abstract

Of the 32 taxa examined, 13 contained 32 spores in each sporangium and are considered apo‐gamous, 14 were sexual species with 64 spores per sporangium, and 5 had 32 spores in some sporangia and 64 in others. When considered as a whole, the spores ranged in size from 29.9 to 74.88μ. Most species had oval or globose spores but several had tetrahedral spores. The spores of all were radially symmetrical. Almost all of the species possessed a crassimarginate type of laesura and all except C. cooperae and C. viscida had a perispore. The ornamentation of the perispore showed the following patterns: napate, granulate, psilate, lobate, foveate, and echinate. The exine pattern was predominantly psilate but foveate, rugulate, napate, and granulate conditions were observed. Seventeen taxa were found to have some degree of spore abortion.

In 1976, one of us (Knobloch) attempted to collate the literature on pteridophyte hybrids. This collation was intended as a service and was not thought to be up-to-date in regard to nomenclature. We included the work of A. J. Retzius in the late 18th century and those ofP. Ascheron, J. DorfIer, H. Christ, R. R. Scott, E. Newman, T. Makino and J. Milde in the 19th century. Some of the names proposed by these earlier workers will now have to be changed. Not all old names have been discarded nor do we feel that all newly-proposed names will stand the test of time.The early part of the 20th century was rather a quiescent period in these matters but from 1950 on, there has been a rather large flood of new investigations in the evolutionary aspects of the pteridophytes. Thus we have need to correct the errors of our previous publication and to add the names of those new taxa which have appeared.Since the present list does not alter the names of accepted hybrid names, it will be necessary, at times, to consult the 1976 publication.We wish to thank the forty persons who have kindly assisted us in ferreting out our errors and in proposing new additions to our list. We especially wish to thank Professor

Confirmatory, corrective and new chromosome counts are listed for species in the genus Cheilanthes, and a new chromosome count is given for a member of the genus Aspidotis. An analysis of five collections of C. castanea revealed no significant morphological differences despite the different chromosome numbers. The ploidy level of all known species in genera of the Sinopteridaceae is summarized, revealing directions in which future research might proceed to complete our cytological knowledge of this family.