1903] CURRENT LITERATURE 153 
paux modes d’agencement dans la fronde,” Bertrand and Cornaille*® describe 
and discuss, from the taxonomic and anatomical standpoint, the consti- 
tution and arrangement of the fibrovascular strands in the leaves of various 
living orders of ferns. They point out that the petiolar bundle-system 
nate ‘‘divergents.”” Each divergent consists of a protoxylem group placed 
anteriorly, z.¢., toward the upper surface of the frond, and two wings of 
metaxylem growing out of this posteriorly, z. e., toward the lower surface 
of the frond. The wood so constituted is typically covered, both dorsally 
and ventrally, by layers of phloem. The petiolar bundle-systems of the 
various groups of living ferns may either be gamodivergent, consisting of a 
number of divergents more or less completely fused together, or dialydiver- 
gent, where the divergents are more or less completely separated from each 
other, In addition the bundle-system as a whole may present various degrees 
of complexity in the curvatures presented by a line drawn so as to connect 
all the bundles in a given petiole, etc. The authors point out that there are 
two striking differences between the petiolar fibrovascular system of the ferns 
{or Megaphyllides as they term them) and that of the cycads; for in the 
latter the fibrovascular units corresponding to the divergents, instead of 
having two wings as in the ferns, are monopolar, and further the protoxylem, 
instead of being placed anteriorly and toward the upper surface of the leaf 
is posterior and next the lower surface of the frond, being thus centripetal as 
in the lycopods. The authors are of the opinion that there should, as a con- 
sequence of these differences, be a good deal of reserve in the matter of 
deriving the cycads from a filicineous stock, as is the almost universal tend- 
ency at the present time.— E. C. JEFFREY. 
THE formation of the spores in Rhizopus nigricans and Phycomyces nitens 
is described by Swingle in a recent Budletin” of the Bureau of Plant Industry 
Pure.cultures were obtained, the material was fixed, sectioned, and stained, 
according to the most approved cytological methods. The paper deals 
especially with the mechanics of the peculiar cell division found in these 
sporangia, and with the nature and functions of the vacuole. It is of interest 
to note that the four genera of the Mucorineae which have now been care- 
fully investigated, Pilobolus and Sporodinia studied by Harper, and Rhizopus 
and Phycomyces studied by the present writer, differ considerably in the 
formation of their spores. The following is Swingle’s own summary of the 
process : 
"8 BERTRAND, C. E., and CORNAILLE, F., Etude de quelques caractéristiques de la 
structure des Filicinées actuelles. Travaux et Mémoires de |’Université de Lille ro: 
—. 1902 
*9SWINGLE, DEAN , The formation of ae in the sporangia of Rhizopus 
nigricans and ane nitens. U. S. Dept. of Agric., Bureau of Plant Industry. 
Bull. 57. pp. 40, Als. 6. 1903. 
