91 SUMMARY OF CURRENT RESEARCHES RELATING TO 
or a formation of thorns. The pith is usually composed of thin-walled 
cells, which, when lignified, have large round pits. 
C4) Structure of Organs. 
Microsporange of Stangeria.* — From a study of the development 
of the male organs in Stangeria paradoxa, Mr. W. H. Lang concludes 
that the arrangement of the sporanges in sori, and the mode of develop- 
ment of the latter, agree closely with Angiopteris (Marattiacese) ; while, 
on the other hand, the origin of the sporogenous cells from the hypo* 
dermal layer, a distinct epiderm being present, is quite different from 
what takes place in any Vascular Cryptogam hitherto investigated ; and, 
except from the small number of sporogenous cells, is similar to their 
origin in the pollen-sac of an Angiosperm. 
The microsporanges are arranged in sori, the development of which 
is similar to that in Ceratozamia ; sometimes the sporanges remain for a 
time united in pairs. The sporogenous cells, usually four in number, 
are derived by periclinal division from cells of the hypodermal layer ; 
the superficial cells take no part in their formation. The tapete arises, 
when the sporange has attained a considerable size, from the outer cells 
of the sporogenous mass. Isolated cells throughout the sporogenous 
mass undergo sterilisation. The structure of the epidermal layer of the 
wall and the mechanism of dehiscence present close resemblances to An- 
giopteris ; stomates are found on the sporange. In the pollen-grain two 
cells are cut off from the large vegetative cell before germination. In 
the later stages of development the ovule resembles that of other 
Cycads. 
Pollen of Asclepias.f — Miss F. E. Langdon states that in the pollen 
of Asclepias Cornuti the archespore is composed, as in most Dicotyledons, 
of a layer of cells, and not, as has been stated, of a single column. The 
tapete is composed, from an early stage, of two or of several layers, never 
of a single layer. The outer wall of the pollinium is derived partly 
from a secretion from the tapete, partly from the outer walls of the 
pollen-cells. The cells of the tapete undergo remarkable changes during 
the development of the pollen, forming a secretion which serves as a 
protection to the pollen. 
Structure of Seeds. — Herr A. Tschirch J states that the ovule of 
mustard ( Brassica nigra ) has two integuments, of which, when ripe, the 
outer consists of 3, the inner of 6-8 rows of cells. These latter consti- 
tute the nutrient layer, giving up their starch, and then more or less dis- 
appearing. In cacao-seeds the layer which has generally been regarded 
as endosperm is really perisperm. In Melampyrum pratense the appen- 
dage at the base of the seed is not a caruncle or a strophiole, but belongs 
to the endosperm. The ovule has only one integument, and even this is 
partially obliterated in the ripe seed. 
Herren A. Nestler and J. Stoklasa § describe in detail the anatomy 
* Ann. of Bot., xi. (1897) pp. 421-38 (1 pi.). 
t Bot. Gazette, xxiv. (1897) p. 189. 
X Schweiz. Wochensehr. f. Chem. u. Pharm., xxxv. (1897) No. 17. See Bot. Cen- 
tralbl., Ixxii. (1897) p. 107. 
§ Zeitsckr. f. Zucker-Industrie in Bohmen, xxi. (1897) p. 8S3. Sec Bot. Cen- 
iralbl , Ixxii. (1897) p. 120. 
