72 SrilMAEY OF CUEEEXI RESEAECHES RELATING TO 



plac€ onlv as a secondary result in parencliTmatous cortical cells. 



But we haTe not yet sufficient knowledge to divide collenchymatous 

 tissue on this ground into subsections. 



C'jllencliymatous cells differ in one rery essential point from true 

 ba~:-e Ls. While in the latter the limit of elasticity nearly coincides 

 with alsjlute firmness, in collenchyma the elasticity is overcome by 

 a comparatively small strain, the firmness only when the strain is 

 increased three or fourfold. 



Since, therefore, a j^ermanent elongation results from the tension 

 to which the collenchyma is subjected in the young turgid internodes 

 and leaf-stalks, but no rupture, it is clear that this tissue can, in con- 

 sequence of its great absolute firmness, afford the necessary assistance 

 to the intercalary construction of these organs, without however 

 interfering with their growth in length. That the growth in length 

 of the collenchyma itself is a consequence of this tension caused by 

 the turgidity of the other parts of the tissue, can scarcely be doubted. 

 But whether the permanent elongation of the collenchymatous parts, 

 caused by the passing of the Kmit of elasticity, plays any definite 

 part in this process, must remain undecided in the present imperfect 

 state of our knowledge of the processes of growth in the cell-walls. 



Epidermis of the Pitchers of Sarracenia and Darlingtonia,* — 

 Prof. A. Batalin has made a careful anatomical examination of the 

 pitchers of Sarracenia fiara. purpurea, and lariolaris, and Darlingtonia 

 calif ornic-j. He finds that the lower region of the iimer epidermis, 

 the " detentive surface " of Hooker, has no cuticle ; while all the 

 other cells of the detentive stirface have one, and especially the long 

 stiff hairs. The inner region of the pitcher is of a uniform bright- 

 green colour within and without ; but this is true of the inner surface 

 only so long as no insects have been captured : it then becomes brown, 

 the green colour of the outside remaining. While on the green spots 

 on the inside of the pitcher the moderately thick and nearly colour- 

 less outer walls of the epidermal cells are quite smooth, at the brown 

 spots, where insects have come into contact with them, they have one 

 or more irregular spots of a much lighter colour. Treatment with 

 chlor-iodide of zinc causes these spots, but not the rest of the cell- 

 walls, to turn blue. 



This observation leads to the conclusion that the contact of an 

 insec-t with the epidermal cells causes a change in the latter, which 

 consists chiefly in the excretion, between the cuticle and the cellulose- 

 wall, of a fluid, the nature of which has not been determined, but 

 which probably has the property of dissolving albuminoids. It 

 appears to act both mechanically and chemically upon the cuticle, 

 forcing it outwards, and finally rupturing and almost entirely destroy- 

 ing it. A change is at the same time taking place in the cellulose- 

 wall. It assumes a brown colour, and in addition becomes partially 

 mucilaginous. 



The author also describes a peculiar sieve-like disk between the 

 epidermis and the glands of Tinguicnl<x vulgaris, 



• Acta Hort. Petrop.. tIL (1880) pp. 3i3-60 (1 pi.). See Bot. Centralbl.. vii. 

 (1881) p 327. 



