224 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Dahlia, Cirsium, and Pseonia, the secondary growth produces a secondary 
meristem, chiefly on the xylem side ; the new masses of tissue are not 
usually lignified. The development of the secondary epidermal tissue 
varies greatly. In Oxalis there is no formation of cork. In Dahlia 
the phellogen is formed from the primary cortex. The primary 
epidermal tissue may pass into the permanent condition by suberization 
of the epiderm and exoderm ; or the tuber is protected outwardly by 
formation of periderm. The formation of cork may be accompanied or 
not by a throwing off of phelloderm. The phellogen originates either 
in the primary cortex or in the pericambiura. 
The structure of the conducting tissue varies according as it is 
intended for the transport of water or of plastic substances ; the number 
of vessels is always small. The strengthening elements, bast-fibres, and 
- libriform are also greatly reduced. The reserve-system is distinguished 
by a great development of active parenchyme. Calcium oxalate and 
tannins are excreted abundantly. 
B. Physiology. 
Cl) Reproduction and Embryology. 
Embryology of Flowering Plants.* — Dr. M. Westermaier has 
investigated the processes which take place in the embryo-sac after 
fertilization — chiefly in certain Ranunculacese and Gramineae — especially 
in relation to the function of the antipodals. In Nigella (sativa and 
damascena ), the antipodals come finally to occupy a lateral position in 
the embryo-sac, nearer to its micropylar than to its chalazal end, owing 
to the unilateral growth of the sac. The same is the case in many 
Gramineae. The swollen appearance of the antipodals, and the mode of 
distribution of the starch in these cases, indicate that antipodals are not 
mere functionless survivals, but play an important function in the 
formation of the endosperm-cells and in the conveyance of nutrient 
materials to the growing embryo. In other cases ( Zea Mays, Salvia 
pratensis, and many other Dicotyledons and Monocotyledons), the part 
played by the antipodals appears to be less important ; though here also 
it is not without significance ; they occupy the chalazal extremity of 
the embryo-sac, and must be regarded as the portion first formed of 
the endosperm-tissue. 
Embryology of Gnetum.t — Pursuing his investigations on this 
subject, Herr G. Karsten describes in detail the development of the male, 
of the imperfect female, and of the perfect female flowers. The first 
division of the pollen-mother-cells originates from a contraction of the 
chromatin framework of the nucleus. The imperfect female flowers 
form a terminal whorl in the male inflorescence. About twenty free 
parietal nuclei are formed in the embryo-sac. When these disappear, a 
drop of fluid exudes from the micropyJe, which probably served, in the 
first place, to detain the pollen-grains carried by the wind, while it now 
performs the function of a nectary. This temporary embryo-sac attains 
* Nova Acta Acad. Cses. Leopold-Carol., lvii. (1892) pp. 1-39 (3 pis.). Cf. this 
Journal, 1891, p. 766. 
t Beitr. z. Biol. d. Pflanzen (Cohn), vi. (1893) pp. 337-82 (4 pis.). Cf. this 
Journal, 1892, p. 506. 
