252 SUMMARY OF CURRENT RESEARCHES RELATING TO 



power of producing resting- spores, and being propagated in this manner 

 only. It is the presence of these parasitic gcmmules that stimulates into 

 increased activity the protoplasm of the cells themselves. 



The author describes the method by which he was successful in 

 infecting healthy roots of the bean by placing them in contact with 

 diseased tubercles ; and finally combats Brunchorst's and Tschirch's 

 view,* that the so-called " bacteroids," or bacterium-like particles, always 

 found in the cells of the tubercles, are modifications of the protoplasm of 

 the cells. 



Emergences on the Roots of Podocarpus.f — Dr. T. A. Baldini has 



investigated the structure of peculiar bodies already described by Van 

 Ticghem on the roots of several species of Podocarpus. In all the species 

 they are of endogenous origin, springing from the second or third layer of 

 cells below the epidermis ; they are formed by walls, the earlier of which 

 are tangential, the later radial. As regards their function, the author 

 believes this to be the absorbing and storing-up of water from the soil. 

 They may also serve as reservoirs for starch and other formative 

 substances. 



Stipules.} — M. G. Colomb states that stipules are of such various 

 forms, and occupy such different positions in relation to the leaf, that it 

 is hardly safe to define a stipule from external characters alone. The 

 author has therefore studied the anatomical structure of this organ in 

 many plants belonging to different natural orders, the details of which 

 are given in this paper. He describes a stipule as an incomplete axillary 

 ligule, and draws the following conclusions from his researches : — 



Three regions may be recognized in a ligule, viz. : — (1) The lateral 

 region, in which the marginal bundles of the sheath are simply prolonged. 

 (2) The stipular region, where the bundles form a part of the last bundle 

 of the sheath entering the leaf. (3) The axillary region, which unites 

 the two stipular regions. 



If the ligule is complete with its three regions, the author has given 

 to it the name of axillary ligule ; if the stipular and axillary regions 

 only are present, the sheathing regions having disappeared, it is an 

 axillary stipule ; but if finally the axillary region is divided lengthwise 

 into two halves, the one on the right and the other on the left, and the 

 stipular regions exist solely at the base of the petiole, it is then an ordinary 

 stipule. 



Stipule and ligule are then organs of the same nature, between 

 which it is possible to find every variety of modification, the stipule being 

 a portion of the axillary ligule. A stipule can be defined as an appendix 

 inserted on the stem, at the base of the leaf, the bundles of which belong 

 exclusively to the corresponding foliar bundles. 



Vernation of Leaves.§ — Herr R. Diez classifies the various modes 

 of the vernation of leaves under a number of different heads, viz. : — 

 Flat (Viscum) ; apposite (zusammengelegt) (Prunus Laurocerasus) ; im- 

 perfectly apposite (Fagus) ; apposite and rounded (Parnassia palustris) ; 

 wedge-shaped ( Veronica Andersoni) ; folded and radiate (Acer plat anoides) ; 

 folded and acute-angled (Pritchardia filamentosa') ; folded lengthwise and 

 curved (Dioscorea villosa) ; folded across and curved (Castanea). These 



* See this Journal, 1887, p. 610. f Malpighia, i. (1887) pp 474-7. 



X Ann. Sci. Nat., vi. (1887) pp. 1-76. 



§ Flora, lxx. (1887) pp. 483-97, 499-514, 515-80 (1 pi.). 



