140 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
first of these functions being indicated by the presence of chlorophyll 
in the guard-cells. He supports the view of Schwendener,* that the 
opening and closing of the stomates is brought about by changes in the 
turgor of the guard-cells, rather than that of Leitgeb,t that an important 
part in this process is played by the adjacent colls ( Nebenzellen ), whether 
these be of the form of ordinary epidermal cells or not. In opposition 
also to Leitgeb, he finds the stomates to be always closed at night ; light is 
the only factor in causing the opening of the stomates, and acts through 
the increase of turgor due to the assimilation of the guard-cells. Stahl’s 
“ cobalt-test ” for the intensity of assimilation J the author does not 
regard as wholly satisfactory in determining whether the stomates are 
open or closed. 
Tubers of the Artichoke. § — According to Herr G. Meyer, the tubers 
of the artichoke are formed by the thickening of the lowermost of the 
stolons which spring from the underground stem. This thickening is 
due to the activity of the original cambium which produces new masses 
of parenchyme ; to the production of parenchyme from interfascicular 
cambium ; and to the subsequent elongation of the parenchymatous cells. 
Glucose is found in the young tuber ; inulin is a subsequent formation, 
both in the tuber and in the aerial plant ; starch is found in the vascular 
bundle-sheath, and disappears only in the autumn from the lower part 
of the tuber. 
j8. Physiology. 
(1) Reproduction and Embryology. 
Fertilisation of Salisburia.|| — According to Dr. S. Hirase, the mode 
of impregnation of Salisburia adiantifolia (Ginglco biloba) differs from 
that of other Conifers, being effected by antherozoids formed within the 
pollen-tube. The two nuclei resulting from the final division of the 
generative nucleus of the pollen-tube become transformed, before enter- 
ing the oospliere, into motile antherozoids. These differ somewhat in 
form from the antherozoids of the higher Cryptogams. They are ovoid, 
82 /x long by 49 fx broad; the nucleus is placed in the middle, and is 
entirely surrounded by cytoplasm. The head consists of three spiral coils, 
which are never completely unrolled, and on them are seated a number 
of cilia ; there is also a sharp tail. As soon as the antherozoids have 
escaped through the apex of the pollen-tube, they swarm with a rapid 
twisting movement. The attraction-spheres which accompany the final 
division of the pollen-tube-nucleus were well observed. 
Fertilisation of Cycas.^ —Prof. S. Ikeno has made a similar obser- 
vation with respect to the mode of impregnation in Cycas revoluta. The 
antherozoids are somewhat larger than those of Salisburia , and consist of 
a central nucleus completely surrounded by cytoplasm. The head is 
composed of four coils, and bears a large number of cilia. Two nuclei are 
found in each pollen-tube, resulting from the division of the generative 
* Of. this Journal, 1882, p. 216. f Op. cit., 1887, p. 261. 
J Op. cit , 1895, p. 130. 
§ Ber. Deutsch. Bot. Gesell., xiv. (1896) pp. 317-62 (1 pi.). 
|| Bot. Centralbl., lxix. (1897) pp. 33-5. Of. this Journal, 1896, p. 328. 
Tom. cit., lxix. (1897) pp. 1-3. 
