THE FUNDAMENTAL TISSUE. 



105 



chamcpcy parts sus (B) the axial cylinder, which consists of several fibro-vascular bundles 

 is surrounded by a thick layer of greatly thickened prosenchyma ; in the young stem the 

 cells are similar to those of Selaginella ; but here also an enormous thickening adds to 

 the prosenchymatous form of the cells of the fundamental tissue ; this is also enveloped 

 by a layer of tissue, the cells of which are thin-walled and not prosenchymatous ; this 

 layer is a descending continuation of the fundamental tissue of the leaves, which enve- 

 lopes the stem everywhere and is itself covered by an evidently developed epidermis. 



(c) 'T/?e Cells and Tissues of the system of the fundainental tissue have not yet under- 

 gone a comparative and comprehensive investigation, like those of the fibro-vascular 

 bundles. Out of the very scattered material I select the following for the information 

 of the beginner. 



Irrespectively of many altogether special phenomena, it is chiefly in connexion with 

 the true epidermal tissue on the one hand and the fibro-vascular bundles on the other 

 hand that the differentiation of the fundamental tissue takes place ; certain forms 

 of this tissue occur as strengthenings, or at least as accompaniments of the epidermal 

 tissue, and have already been described as Hypoderma ; other masses of tissue accompany 

 the separate fibro-vascular bundles as partially or entirely closed envelopes or sheaths, 

 which I term generally Bundle-sheaths. In the same manner the whole remaining 

 internal space of the organ con- 

 cerned is commonly filled up by 

 other forms of tissue, which do not, 

 as for the most part the two former 

 do, occur in the form of layers, but 

 in masses ; these I will designate 

 simple Intermediate Tissue (Fiillge- 

 webe). Each of these combinations 

 of tissue may be composed of very 

 different forms. 



The Hypoderma appears some- 

 times as thin-walled succulent watery 



tissue (as m leaves 01 1 radeSCantiaand fig. SS.— Transverse section through the underground stem of Pterzs 



Bromeliacex ). I n Dicotyledons (stems T"^''-'^ ' '• '°°'-''^'''^ • . ^""""^'y '•"'^kened brown-waiied ceiis beneath 



^ ^ ^ the epidermis ; y one lymg deeper and less strongly thickened ; a part 



and leaf-stalks) it commonly consists of the wall is seen in front ; j^cells of the deeper layers containing starch. 



forming the passage to the inner colourless parenchyma of the funda- 

 mental tissue. 



Fig. 89.— Transverse section of the acicular leaf of Pinus 

 Pinaster (x about 50) ; e epidermis; es hypodermal fibrous 

 bundles ; sp stomata ; h resin-passages ; gb colourless inner 

 tissue containing two fibro-vascular bundles. 



Fig. 90.— The left-hand corner of the previous figure mag 

 nified (800) ; c outer cuticularised layers of the epidermis- 

 cells ; i inner non-cuticularised layers ; C very strongly thick- 

 ened outer wall of the epidermis-cells situated at the corner; 

 ^zthe hypodermal cells ; g the central lamella: i' the stratified 

 thickening-mass ; p parenchyma containing chlorophyll ; pr its 

 contents contracted. 



longitudinally extended, narrow, and thickened in the angles by a mass capable of great 

 swelling ; or the hypodermal fundamental tissue is developed in a sclerenchymatous 



