740 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
is formed by the outer part of the external integument of the ovule. In 
plants where there is only one integument, the envelopes of the seed are 
either formed from this integument only or from the integument and the 
nucellus. Sometimes the lignified portion of the seed takes its origin 
from the epiderm of the nucellus. 
Extra-floral Sectaries of Sambucus.* — Dr. U. Dammer finds in 
Sambucus nigra four different kinds of extra-floral nectary. Between 
each pair of leaves are a pair of curved narrow structures with glandular 
apex, which are metamorphosed stipules. In addition to these, the 
lower pinnules of the primary pinnae, and the ultimate divisions or 
teeth of the pinnae, may be transformed into nectariferous bodies ; and 
interpolated between the stipular nectaries are occasionally found other 
bodies of the same character, which may be of the nature of excrescences. 
Cladodes of Ruscus aculeatus.j ; — M. W. Bussell describes the 
development and anatomy of the cladodes of Buscus aculeatus. Formerly 
this organ was considered as a leaf ; but Turpin, in 1820, distinguished 
it as a leaf reduced to the rudimentary state of a flattened branch. In 
1840 Martins gave it the name of cladodum, and recent writers, with 
few exceptions, have considered it as a flattened branch, and of the same 
nature as those found in Xylophyllum and Miihlenbeckia. Van Tieghem, 
however, in 1884, from the disposition and orientation of the bundles, 
concluded that it represented a leaf united with the axillary branch from 
which it proceeded. The author then describes the anatomy of a branch 
of Buscus , and calls attention to the terminal bifurcating cladode, under 
which is seen the flattened branch. In conclusion, the development 
shows that the floral peduncle is a branch of the second generation, and 
the comparative anatomy of the terminal and of the lateral cladode 
proves that this organ is neither a leaf nor a leaf united to the 
axillary branch from which it proceeds, but that it is a flattened branch. 
Spines and Thorn s.J — Herr H. Mittmann classifies the various forms 
of spiny protuberances which serve to protect plants from the attacks 
of animals under the following heads: — (1) Root-spines; (2) Stem- 
spines, which may be either metamorphosed axillary or supernumerary 
buds ; (3) Leaf-spines, the whole leaf, stipules, or portions of the leaf ; 
(4) Trichome-spines, either from the periblem or from the dermatogen ; 
with transitional forms between these. Examples of each of these 
forms are described, including the solitary case of root-spines, the palm 
Acanthorhiza acnleata. 
The special common characteristics of spiny structures are the 
strong development and peripheral position of the mechanical tissue, 
which increases in strength from the base towards the apex, and the 
strong thickening and lignification of its cells ; a corresponding reduc- 
tion of the assimilating and conducting tissues; and the peculiarity, 
which is especially characteristic of stem-spines, that grow r th continues 
longest at the base of the organ, the apex being the oldest portion, and 
that which arrives soonest at maturity. 
* Oesterr. Bot. Zeitschr., xl. (1890) pp. 261-4. 
t Bev. Gen. de Bot. (Bonnier), ii. (1890) pp. 193-9 (10 figs.). 
j Abhandl. Bot. Ver. Brandenburg, xxx. (1889) pp. 32-71 (2 pis.). 
