C>4 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tlie opinion which has been expressed by some writers, that their main 
purpose is to prevent the access of rain to the nectary. 
Variations in the Structure of the Acorn.* * * § — Prof. G. Stenzel de- 
scribes the variations in the structure of the fruit of Quercus pedunculata 
in the following points : — (1) In their size and shape ; (2) In the unequal 
size of the cotyledons ; (3) In the variable number of the cotyledons, 
which may be reduced to one either by the suppression of one or by 
coalescence, or may be increased to three or rarely to four ; (4) In the 
lateral position of the plumule ; (5) In the occurrence of two, or more 
rarely of three seeds in the ovary; (6) In polyembryony ; more than 
two embryos were never observed. 
Buds of Sempervivum and Sedum.f— Prof. A. Kerner v. Marilaun 
describes the structure of the buds which detach themselves for the pur- 
pose of propagation from Sempervivum arenarium and soboliferum and 
Sedum dasyphyllum. In the species of Sempervivum minute buds are 
formed in the axil of the leaves of the rosette ; these put out filiform 
stolons, the ends of which are densely covered with leaves ; these globular 
terminal portions become detached by the withering of the lower part of 
the stolon, are blown away, and develope into new plants. In Sedum 
dasyphyllum it is not uncommon for the flowers themselves to be meta- 
morphosed into a rosette of small leaves ; or buds may be found imbedded 
in the tissue of the upper surface of the very thick leaves of the central 
portion of the stem, or elevated on long stalks in the axil of the lower 
leaves. All these become detached and germinate in the same way. 
Dormant Buds in Woody Dicotyledons.* — M. A. Prunet states that 
all woody plants have dormant buds, but that these buds are often 
very small, and hidden in the bark ; microscopical examination is fre- 
quently necessary to determine their existence. Their connection with 
the pith of the stem is by means of a large medullary ray. These dor- 
mant buds are not only met with in the axil of ordinary leaves, but at 
the base of rudimentary leaves and bud-scales ; and one or more addi- 
tional buds often accompany the normal axillary bud. In exceptional 
cases the additional buds may appear opposite the point of emergence 
of the lateral foliar traces, in the axil of the plurifascicled leaves. The 
duration of dormant buds depends upon their means of defence against 
the sources of destruction, especially desiccation. 
Leaves of Nymphseace9e.§ — Prof. G. Arcangeli describes the structure 
of the submerged, aerial, and floating leaves of Nymphsea alba and 
Nuphar lutea , which agrees with the well-known features of the leaves of 
other water-plants. The formation of submerged leaves only in great 
depths he does not regard as the direct result of the greater depth of 
water, but rather as due to a weakening or decrease of vital energy, 
resulting from the greater depth of the roots below the surface. 
* Luerssen u. Haenlein’s Biblioth. Bot., Heft 21, 1890, pp. 4G-G5 (1 pi.). 
t Oesterr. Bot. Zeitschr., xl. (1890) pp. 355-7 (5 figs.). 
X Journ. de Bot. (Morot), iv. (1890) pp. 258-G3. 
§ Nuov. Giorn. Bot. Ital., xxii. (1890) pp. 441-6. 
