ISO SUMMARY OF CURRENT RESEARCHES RELATING TO 



a velvety texture owing to a thick growth of delicate downwardly 

 directed hairs. These trichomes arise as outgrowths from the outer 

 walls of the young epidermal cells : at a later stage they assume an 

 outward and downward course, and have a well developed basal attach- 

 ment. The outer side of each hair is covered with a ribbed cuticle and 

 usually has no pore, although a single pore is sometimes found in the 

 angle of the bend. The adjacent cell-membrane is strongly thickened 

 when fresh and has a complex of pores towards the interior of the leaf. 

 When dead, the hair-membrane breaks and assumes an alveolar structure. 

 It appears as if the old leaf -sheaths forming the tunic act as a reservoir 

 from which the living sheaths adjoining it take up water, and so render 

 the plant less dependent upon the water in the soil. The author con- 

 siders that further work in this direction will furnish interesting and 

 useful results 



Reproductive. 



Fruit-wall of the Papilionaceae.* — M. Fucsko has studied the 

 structure and development of the fruit-wall of the Papilionaceas, and 

 distinguishes two chief types, viz. the older and simpler type of pod 

 found in such genera as Trifolium, Galega, Goronilla, etc., and the 

 legume of Pisam, Vicia, Genista, etc. The development shows that 

 the outer part of the double hard layer belongs to the mesocarp, while 

 the inner part, and also the entire layer when the latter is simple, is 

 derived from the inner epidermis. The growth of the pericarp and the 

 seed is not equally rapid ; during the early stages the pericarp grows 

 more quickly, but subsequently the seeds grow at a greater rate. The 

 distribution of the forces governing the torsion of the valves is as 

 follows : The transverse swelling-force of the fibres increases until it 

 reaches a maximum in the middle of the layer and gradually decreases 

 towards the inner surface : the longitudinal force is least in the centre 

 and greatest in the outer part of the hard layer. Thus, each hygro- 

 scopic bend is the resultant of these two factors, but is more evident 

 in the outer part, since the greatest torsion is there. The resulting 

 displacement is gradual and symmetrical on both sides of the pericarp. 

 The torsion of the fibres themselves plays an active part in the general 

 torsion : the inner and outer fibres twist in opposite directions, but 

 neither in direction nor amount is their torsion symmetrical in the two 

 halves of the pericarp. The torsion of the inner fibres decreases the 

 general torsion, since it is of greater strength than that of the outer 

 fibres. Thus, the movement of the valves is not a simple transverse 

 twisting, but a bending and torsion resulting from the swelling of the 

 hard layer and torsion of the individual fibres, the latter being sometimes 

 a retarding force and at others an increasing force. 



Embryo-formation in Balanophora.f — A. Ernst has studied the 

 formation of the embryo in different species of Balanophora, and finds 

 that the embryo-sac is derived directly from the embryo-sac-mother-cell, 

 or arises, after a single division, from the upper daughter-cell ; the 



* Flora, vi. (1913) pp. 160-215 (24 figs.). 

 t Flora, vi. (1913) pp. 129-59 (2 pis.). 



