322 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Germination of Onguekoa and Strombosia.* — E. Heckel, continuing 

 his studies on the seedlings of Olaeaceae, finds that similar methods are 

 followed in the West African genus Ongnel-oa, and in some species of the 

 Malayan Strombosia, to that previously described in Ximenia americana. 

 The cotyledons remain included in the seed in all three genera. In 

 Onguelcoa and species of Strombosia there is a great elongation of the 

 hypocotyl, and the seed is carried far above the ground ; in the African 

 genus, and in Strombosia javanica, the cotyledons become separated from 

 the aerial axis at their points of insertion, and fall to the ground with 

 the seed. 



Cockscomb Fasciation of Pine-apples, f — J. W. Harshberger de- 

 scribes some striking cases of fasciation in this fruit, the larger of which 

 were apparently composed of a dozen or more individuals. A photo- 

 graphic reproduction is given of one of the largest specimens. 



Physiology. 

 Nutrition and Growth. 



Theory of the Shifting of Lateral Organs through Mutual Pres- 

 sure. J — L. Jost maintains that Schwendener's theory of "shifting" of 

 organs during growth, and of stem-torsion, will not explain such altera- 

 tions in arrangement as he himself now describes in the case of leaves 

 of conifers and florets of the sunflower. Actual shifting, in the sense 

 that in the young condition of a plant other organs are in lateral contact 

 than in an older condition, was never observed, and the author main- 

 tains that there are to-day in the province of botany no facts known 

 which render necessary the assumption of a subsequent shifting, in 

 Schwendener's sense, of organs whose position has once been defined. 



Influence of Tension and Pressure on the Direction of the Cell- 

 wall. § — L. Kny draws the following conclusions from his investigations 

 on the growth of various members of different plants. The tensions set 

 up in parts of plants which are still capable of growth, and exercising 

 either a pull or a pressure on the individual cells, are responsible for 

 the direction of the prevailing cell-growth and for the position of the 

 division-walls. Growth takes place, in so far as other forces do not 

 prevent, in the direction of the pull and at right angles to the pressure. 

 "When cell-division occurs the dividing walls tend to lie in the direction 

 of the pressure and at right angles to the pull. Opposing forces may be 

 external or internal. The most important external forces are represented 

 by mechanical obstacles with which certain tissues and plant organs (e.g. 

 stems of lianes, roots, &c.) have to contend. Light may, as in the case 

 of germinating spores of Equisetum, have an important influence on the 

 position of the dividing wall. The author regards as an internal force 

 the course of development prescribed by heredity for the species in 

 question. An example of the overpowering of the action of pull and 

 pressure by such internal forces is found in the early stages of periderm 



* Compt. Rend., exxxiv. (1002) pp. 4S9-90. 



+ Proc. Acad. Nat. Sri. Philadelphia, 1901, pp. G09-11. 



$ Bot. Zeit., lx. (1902) pp. 21-43. 



§ Pringsh. Jahrb., xxxvii. (1901) pp. 55-9S (2 pis.). 



