KTJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 



Modifications of these ty- 

 pes occur. In P. Robbinsii, for 

 instance, we meet with a by- 

 form of the prototype caused by 

 the particular compressed form 

 of the stem. See tlie account 

 of this species and the Fig. 19. 



P. lucens, the stele dia- 

 gram of wich properly belongs 

 to the oblong type, like that 

 of P. gramineus, varies on ac- 

 count of the plant's being part- 

 ly a sclerenchymatous species 

 partly a coarse-grown form, 

 which is in need of special cau- 

 line vascular bundles. Accor- 

 dingly you will sometimes find 

 a couple of cauline bundles in 

 the lateral areas at the same 

 time as the dissolution of the 

 xylem of the two median bund- 

 les is incomplete and a more 

 or less thin partition between 

 them is left in the central ca- 

 vity. But the typical state is 

 three large canals along the 

 axial diameter of the diagram. 



An anatomical stem- 

 diagram, of which is spoken 

 in this paper, means a sketch 

 of the stem-anatomy such as 

 it appears in a cross-section 

 at about the middle of an in- 

 ternode a few internodes be- 

 neath the primary spike. The 

 constituents of this diagram are 

 the following parts: 1) epider- 

 mis, 2) its strengthening stratum 

 or the subepidermal bark-layer, which rather improperly may be caUed hj'poderma,^ 

 3) accidentally' existing subepidermal (pseudo-hypodermal) bast bundles or strands, 



A — By The prototypic difigr. 

 tho median bundles and the 

 noflosus PoiR., median bnnd- 



Fig. 1. Different types of stele-diagrams. 

 A, P. prwlotu/us WuLF. B, P. Hnguatus Hagstr., 

 interjacent selerenchyma. C, The trio-diagram, P. 

 les, showing the disposition of the phloem, 1, in three parts, 2, in two parts. 

 Z), The eight-bundled diagram, P, var/hwtits Tuncz. 7?, The four-bniidled dia- 

 gram, P. Clieesemanii Benn. F — H, The oblong typo of diagram; F, P. obtnsi- 

 foliHS M. & K.J Gf P. confervoUJes RcnB. //, P. lucens L., 1, typical form, '2, in- 

 stance with a more primeval state. K — L, The circular diagram, K, P. rnli- 

 Itis WoLFG. i, from an internode at the middle of the plant; 2, from the 

 intornode next below the primary spike, showing the spreading again of the 

 lateral bundles from the median ones. L, P. foliostis Raf. showing the central 

 stele laterally somewhat compressed. All ca. '5,'^. — in, median bundles, ^ la- 

 teral bundles, fb, foliar bundles, c, cauline bundles, ctt\ opposite bundle, 

 //•, the trio dissolved or fused to a compound bundle, scl, selerenchyma, p, pith, 

 X, xylem canals; the chequered parts represent the phloem of the ijundles; 

 end, endodermis. 



'■ According to the exposition of tlie liypoderma by some authors (for inst. E. STRASSBtmoEB, Das kleiue 

 bet. Pract. (1893) 0(1 — 67) I use tliis term for tlic stratum concerned as its chief function evidently is to 

 strengthen the epidermis. Otherwise it should be termed pseudo-hypoderma. 



