292 BOTANICAL GAZETTE [APRIL 
Secondary thickening in pteridophytes.—The known cases of secondary 
thickening in recent Pteridophyta have been brought together by HIL1’S in a use- 
ful résumé. After stating the criteria for secondary growth, Botrychium, which 
has a distinct cambium, and Ophioglossum, which lacks a definite layer, are 
described, followed by Angiopteris and Marattia, in which a cambium forms a 
few xylem elements. CoRMACK’s observations on the secondary wood in the 
nodes of Equisetum are cited, though no reference is made to the cambium in the 
young cone as reported by Jerrrey.?4 The other cases of secondary growth 
include Psilotum, Selaginella spinulosa, and several species of Isoetes, especially 
I. hystrix, which may show a cambium outside the vascular cylinder.—M. A. 
CHRYSLER. 
The cell wall.—Whether isolated portions of protoplasm without nuclei are 
capable of surrounding themselves with walls or not has long been in dispute. 
Nearly twenty years ago Pata claimed that isolated portions of protoplasm 
could still form membranes. Later observers claimed that the non-nucleate 
fragments might still be connected with nucleated portions of the protoplasm by 
connecting fibers. Studies of the rhizoids of Marchantia polymorpha and the 
stinging hairs of Urtica dioica bring PALLA*S to reassert his original view that 
non-nucleate portions of protoplasm can form membranes. He admits, however, 
that the portions of protoplasm must contain, as reserve substance, a material 
which can be used in building up a wall.—Cuar es J. CHAMBERLAIN. 
South African cycads.—PEARSON?® has begun the publication of a series of 
field notes on South African cycads, which promise to be of great interest. The 
first paper deals with Encephalartos Friderici Guilielmi, E. Altensteinti, E. 
villosus, and an unnamed species of Stangeria. A summary of the observations 
is as follows: subterranean branching is a marked feature of the first-named 
species and of Stangeria; in the first two species of Encephalartos the strobili are 
lateral, occurring in cycles of three to six about the vegetative apex, which con- 
tinues the growth of the stem; there is evidence that strobili are produced much 
more freely in exposed than in shaded situations; it is probable that entomophily 
occurs in E. villosus.—J. M. C 
Apogamy in Elatostema.?7—Treusp adds Elatostema acuminatum (Urti- 
caceae) to the increasing list of plants in which apogamy has been described. 
a3: Bau, 'T. Ge, oy secondary thickening in recent Pteridophyta. New Phytol- 
ogist 5:208-214. 1 
24 JEFFREY, E. es The ——— structure, and affinities _ the genus Equi- 
setum. Mem. Boston Soc Soc. Nat. Hist. 5:155-190. pls. 26-30. 1 
25 PALLA, E., Ueber prgite ace kernloser Plasmateile. te Deutsch. Bot. 
Gesells. 24:408-414. pl. 19. 1906. 
26 Pearson, H. H. W., es = South African Cycads. I. Trans. S. African 
Phil. Soc. 16: 341-354. pls. 6-8. 
27 TreEvB, M., L’apogamie < eo ateen acuminatum Brogn. Ann. Jard. Bot. 
Buitenzorg 20:141-152. pls. 4-11. 1906. 
