302 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
BOTANY. 
A. GENERAL, including the Anatomy and Physiology 
of the Phanerogamia. 
a. Anatomy. 
(1) Cell-Structure and_Protoplasm. 
Influence of the Nucleus on the Formation of the Cell-wall.* — 
Prof. W. Pfeffer contests the statement of Palla f that an isolated non- 
nucleated mass of cytoplasm can form a cell- wall. This erroneous obser- 
vation has arisen from overlooking connecting threads of protoplasm. 
From observations made on rhizoids and leaves of mosses, prothallia, 
Clfiara , leaves and hairs of flowering plants, pollen-tubes, &c., it would 
appear that the irritation necessary for the formation of a cell- wall is 
caused by the extremely fine protoplasm filaments which 'pass through 
the cell-wall and which constitute a living connection between neigh- 
bouring protoplasts. The same function belongs to masses of cyto- 
plasm which lie in close apposition to a cell-wall, and which there- 
fore maintain their connection with the protoplasmic filaments of tho 
neighbouring cells. The existence and healthy life of an organism are 
dependent on the co-operation of the nucleus and cytoplasm. 
Chromatin-reduction and Tetrad-formation in Pteridophyta.f — 
Mr. G. N. Calkins describes the following phenomena in the formation 
of spores in Pteris tremula and Adiantum cuneaium , tracing their analogy 
to the corresponding processes in animals. The process of spore-forma- 
tion can be divided into the three periods of division, growth, and matura- 
tion. The division period is the interval between the archespore and the 
16-cell stage of the sporange. The growth period is the interval during 
which the 16 cells enlarge, and tetrads are formed. The maturation 
period includes thejjwo successive divisions of the nuclei in the 16-cell 
stage and the formation of the spores. The cells of the division 
period are commonly known as the archesporial cells. For those of the 
growth-period the author proposes to replace the term spore-mother-cell 
by primary sporocyte, using also secondary sporocyte for the daughter-cells 
of the primary sporocyte. In the growth-period the chromatin forms a 
delicate moniliform spireme before the nucleole has disappeared. A 
much thicker spireme is subsequently formed from this moniliform 
thread. The thickened spireme then splits longitudinally. It next breaks 
up into half as many double spireme-segments as there are chromosomes 
in the somatic cells ; each of these double elements forms a tetrad. 
Three types of tetrad-formation are found in each nucleus — the rod 
type, the ring type, and the cross type. In all three types, the tetrads 
are finally formed by a transverse division of the halves of the double 
spireme -segment. 
Cell-Hypertrophies produced by Galls.§ — M. M. Molliard describes 
the pathological hypertrophy of cells caused by the attacks of species of 
* Ber. K. Sachs. Ges. Wiss. Leipzig, 1896 (1897) pp. 505-12. 
f Cf. this Journal, 1890, p. 475. 
i Bull. Torrey Bot. Club, xxiv. (1897) pp. 101-15 (2 pis.). 
§ Kev. Gen. de Bot. (Bonnier), ix. (1897) pp. 33-44 (2 pis.). 
