54 SUMMARY OF CURRENT RESEARCHES RELATING TO 



plants develope tardily and imperfectly, tLe leaves becoming in many 

 cases more or less cblorotised. The production of flowers and fruit 

 is also unfavourably affected. The author claims to bave discovered, 

 generally distributed in the green tissues of plants, quantities of very 

 minute and extremely mobile micro-organisms — micrococci, bacteria, 

 ovoid bodies — which he believes to be of great importance to the life of 

 the plant, having frequently an injurious effect, and being probably one 

 of the causes of chlorosis. 



Viridescence and Fasciation caused by a Parasite.* — M. Molliard 

 recoids an example of viridescence in the flowers of Trifolium repens, 

 and one of fasciation in the stem of Raylianus Haphunislrum ; the 

 former caused apparently by tbe attacks of a parasitic fungus belonging 

 to the Deinatieae, Polythrincium Trifolii, the latter to those of a coleo- 

 pterous larva. 



Stomates on the Upper Side of Leaves.f — E. Kiihne finds the oc- 

 currence of stomates on the upper side of the leaves to be more common 

 in woody plants than has generally been supposed. They were observed 

 in 222 out of 1359 species examined. An attempt is made to connect 

 their occurrence with climatic conditions. 



Stomates of the Box.J — Prof. K. Chodat and M. Bernard describe 

 the peculiar structure of tbe stomates on tbe leaves oi Buxus semper- 

 virens, which somewhat resembles that in Iris. There are usually six 

 modified epidermal cells belonging to each stomate. Tbe power of 

 movement by which the Assure is opened and closed does not reside in 

 tbe guard-cells, but in three hypostoniatic cells which put out papilla* 

 that push themselves up to the Assure. 



Lenticels.§ — H. Devaux has made an exhaustive study of the struc- 

 ture and functions of lenticels, which he finds in all the great grouj>s 

 of vascular plants, and on all their organs where there is secondary 

 growth. Tbe total amount of surface covered by tbe lenticels is, within 

 certain limits, nearly uniform, their size being nearly in inverse pro- 

 portion to their number. 



Three layers may be distinguished in a lenticel, analogous to those 

 of tbe periderm : — a jmelloderm, a suberised layer (or more than one), 

 and an intermediate formative region. Two types are specified, viz. : — 

 (1) those in which the closing layers are thm, and are composed of 

 cells intimately united, with no or only very small intercellular spaces - f 

 and (2) those in which the closing lajers are often thick, and are com- 

 posed of rounded cells with abundant intercellular spaces. 



Lenticels are either primary or secondary ; the former are found at 

 an early period at a point determined by an organ — stomate, root, or 

 bud ; tbe latter are formed later at points not determined by an organ. 

 Wherever there are stomates, there is a tendency to produce lenticels 

 below them in the cortex, sometimes in the pericycle ; they occur 

 normally at the base of young rootlets. The growth of lenticels takes 

 place by a continual proliferation of new rounded elements and tbe 

 suberification of the cells. 



* Rev. Gen. de Bot. (Bonnier), xii. (1!)()0) pp. 323-7 (3 figs), 

 t Mittl). Deutscb. dendiol. Ges., 1899, pp. 47-67. See Bot. Centralbl., lxxxiv. 

 (1900) pp. 13u. X Arch. 8ci. Pays, et Not., ix. (1900) pp. 495-6. 



£ Ann. Sci. Nat. (Bot.), xii. (1900) pp. 1-240 (6 pis. and 7 tigs.). • 







