ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 520 



In a different communication * J. Wiesner states bis general con- 

 currence with Frank's conclusion, which he would carry somewhat 

 further. From its impermeability to organic acids, Wiesner regards 

 protoplasm as having for one of its functions the protection of chloro- 

 phyll from injury from this source. The same process takes place 

 also in fruits as in leaves. 



Latex of Euphorbia Lathyris.j - - — An elaborate examination of the 

 latex of Euphorbia Lathyris has led J. Schullerus to the conclusion 

 that it must be regarded neither as a product of excretion (waste 

 product) nor as a reserve material, but as a substance of actual direct 

 service to the nutrition of the plant. The following are some of 

 the special results at which he has arrived : — 



The laticiferous tubes of this plant originate even in the embryo, 

 and exclusively in the cells contiguous to the cortical parenchyma ; 

 no laticiferous cells being formed at a later period or originating in 

 any other way. They are found during the whole life of the plant, 

 and in all its parts, in the root as well as the aerial portion. They 

 may branch, but do not anastomose, either in the nodes or leaves. 

 The growth of these tubes does not depend on tbat of contiguous 

 cells, but is independent of them and may even be restricted by their 

 growth ; they retain, during their existence, their power of apical 

 growth and of branching at any spot. The latex of E. Lathyris is a 

 formative sap, taking part directly in the processes of growth of the 

 plant, and cannot be regarded as a mere reserve material. Its 

 nutritive properties are proportionate to the amount of carbohydrate, 

 especially starch, contained in it. When in an inactive condition it 

 passes over to the state of a primordial latex. This is also the 

 function of the latex of the permanent rhizomes of Euphorbia palus- 

 tris, orientalis, Pithyusa, and trigonocarpa, rich in albuminoids, but 

 containing but little carbohydrate. The absence of this property 

 of storing up reserve materials distinguishes the laticiferous vessels 

 physiologically from the cortical parenchyma. Besides osmotic 

 movement, the latex possesses also a power of movement in mass, 

 corresponding to the general movement of food-materials towards those 

 parts where new formations are taking place, not due in any way to 

 external influences. 



These facts regarding the physiological function of the latex of 

 E. Lathyris are true also for that of other species of Euphorbia 

 which do not differ from it by any very strongly marked characters. 



Darwin's so-called "Brain-function" of the Tips of Roots.| — 

 E. Detlefsen has investigated in a series of fresh experiments, the 

 peculiar properties attributed by Darwin § to the extreme tips of 



* Bot. Centralbl., x. (1882) pp. 260-6. 



t SB. Bot. Ver. Prov. Brandenburg, xxiii. (1882) pp. 26-93. 



X Arbeit. Bot. Inst. Wiirzburg, ii. (1882) pp. 627-47. 



§ " It is hardly an exaggeration to say that the tip of the radicle thus 

 endowed, and haviDg the power of directing the movements of the adjoining 

 parts, acts like the brain of one of the lower animals ; the brain being seated 

 ■within the anterior end of the body, receiving impressions from the sense-organs, 

 and directing the several movements." — Darwin, The Power of Movement in Plants, 

 p. 573. 



Ser. 2.— Vol. II. 2 N 



