FEE Oe ON Gene Ae ee 
1910] CURRENT LITERATURE 239 
families that he has investigated, he finds that the killing of a short zone of a 
stem or of a petiole results very soon in cutting down the water transport to the 
parts above, and leads to wilting—the longer the killed zone, the quicker the wilt- 
ing. He claims that there is no blocking or interfering with the water path, but 
that the reduced water movement is due to the lack of living cells in the zone 
killed. This indicates that the continuous rise.of sap in small plants, as has been 
shown to be the case in tall trees, is dependent upon the action of living cells.— 
WILirAM CROCKER. 
Seedling structure of Gnetales.—HILt and DEFRAINE*® conclude their account 
of the seedling structure of gymnosperms by a presentation of Gnetales. A 
short cotyledonary tube is formed in every case; the cotyledonary traces are two 
in Ephedra, four (in two pairs) in Welwitschia, and four or five in Gnetum, and all 
the traces are collateral endarch. The so-called foot in W elwitschia and Gnetum is 
described as a parenchymatous growth at the base of the hypocotyl, in the former 
genus being spadelike and with no vascular supply, and in the latter genus being 
rodlike and with numerous well-differentiated bundles. The transition to root 
structure occurs in the lower region of the hypocotyl, in Welwitschia and Gnetum, 
immediately below the foot; and in all cases the primary root is diarch—J. M. C 
‘“‘Apogamy” in Pteris.—Miss STEPHENS and Miss Sykes have examined 
prothallia of Pteris droogmantiana furnished by Booptr. In a brief note’ they 
announce that binucleate cells are common; that there has been no nuclear 
migration, as no surrounding cell is without its nucleus; that the two nuclei arise 
from the division of the nucleus of an ordinary cell without wall-formation; that 
the two nuclei thus produced remain separate for some time and then fuse. Just 
what this performance means is not evident, but perhaps the fuller paper will 
tell. The note is called one on “‘apogamy,” and presumably there is reason for 
knowing that these are apogamous prothallia.—J. C 
Morphology of Psilotum.—SritEs?° has investigated the anatomical structure 
of the serial shoots of Psilotum flaccidum, one.of the two species usually regarded 
"as constituting the genus. Aside from certain anatomical details that distinguish 
this species from the other (P. triquetrum), the main results are that secondary 
thickening is found in this species also; that mesarch structure occurs in the lower 
part of the aerial stems; that the sporangiophore trace terminates in the central 
tissue between the three “confluent” s sporangia, as had been shown for Temes: 
feris; and that no evidence was obtained to decide whether the sporangiophore is 
“foliar” or is “an organ sui generis.”—J. M. C. 
L, T. G., and DEFRarnNE, E., On the seedling structure of gymnosperms. 
8 Hin 
AN, Pe Annie of Botany heise css, pls. 22, 23. 
PHENS, E. L., and SyKes, M. G., Freliminery 4 note on apogamy in Pieris 
droogmantiana, Aue of Botany 24: ie 119: 
20 STILEs, W., Th reset fe f Psjlot ft idum Wall. Annals 
of Botany 242373-397. pl. 25. 1910. 
