702 SUMMARY OF CURRENT RESEARCHES RELATING TO 



whether the aspect is north, ponth, cast, or west; then thcro is the effect 

 of other trees which happen to grow in the immediate neighbourhood ; 

 and finally the influence of curvature or lesions. 



Influence of Exposure on the Formation of the Annual Rings in 

 the Savin.* — M. E. Mer gives the details of a number of observations 

 made to determine the influence of exposure on the formation of the 

 annual rings in the savin. The results may be st ited in the fact that 

 nutrition had evidently been made much more active on the east side of 

 the trees than on the west. A southern exposure had produced an 

 analogous though less accentuated eft'ect upon the cambium than a 

 westerly one. One of the tables shows the difference in the breadth of 

 the annual rings east and west. 



Mai nero of the Vine.f — Sig. 0. Comes has studied the cause of the 

 " mal nero " or gummosis of the vine, and finds it to be characterized by 

 the presence of brown corpuscles in the amyliferous parenchyma, which, 

 though described by some writers as elements of solid tannin, he regards 

 as produced by gummy degeneration of the starch-bearing cells. 



(4) Structure of Organs. 



Formation of Lateral Roots in Monocotyledones.i — In further 

 instalments of this paper Prof. A. Borzi describes a second type of tlie 

 lateral roots of Monocotyledons, in which the meristem is composed of 

 only three distinct kinds of initial cells, producing the plerome. the 

 periblem, and the root-cap, the dermatogen being a dependency of the 

 periblem. He describes in detail the structure of the root in Elegia 

 deusta and Scirpus laciistris. In the former case the pericambium is 

 constituted of a double row of cells, and this type is characteristic of 

 the CyperaceaB, Gramineae, and Musacea3. 



In a third type the growing apices of the radicles are made up of 

 two distinct kinds of initial cells ; the one are the common origin of the 

 periblem, dermatogen, and root-cap, the other of the plerome. Examples 

 of this type are furnished by Bichardia afiicana and by a number of 

 other Aroidea>. 



In the fourth type the apex of the cone of growth with the initial 

 cells are the common origin of the plerome, jicriblem, and dermatogen, 

 and normally also of the root-cap. This may again be divided into two 

 subdivisions : — in the first the root-cap is altogether distinct from the 

 other histogenous elements of the cone of the root. This occurs in 

 Sparaxis versicolor and in many other Irideae. In the second subdivision, 

 of which Lilium candidum may be taken ag an example, the root-cap is 

 not distinct from the apex of the cone of growiih. Here the initial rows 

 of plerome give birth to the periblem, the outer layers of which are con- 

 verted into the root-cap. The endoderm of the root forms the dermatogen, 

 laterally to the nascent cone of growth, and, in the region of the apex, a 

 thin temporary protecting sheath. In a further stage of development 

 the increase of the growing apex of a radicle takes place by means of 

 initial cells situated at the apex of the plerome-cylinder, which, as long 

 as they renew this cylinder, generate the periblem. The outer central 



• Morot's Joum. de Bot., ii. (1888) pp. 165-70, 184-91. 



t Atti R. Ist. d'lncoraggiamento alle Sci. Nat., 1887. See Eev. Mycol., x. (1888) 

 p. 165. X Malpighia, i. (1S87) pp. 541-50; ii. (1888) pp. 53-85. 



