KUNGL. 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 tliat 

 of P. gramineus, varies on ac- 

 count of the planfs 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 2 sc l 

 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 Spöken Fig. I. Different types of stele-diagrams. A— B, The prototypic diagr. 



,, . , , A, P. jn-ielongus Wolf. B, P. linguatus Hagstr., the median bundles and the 



in tlllS paper, meanS a SketCll interjacent sclerenchyma. C, The trio-diagram, P. nodosus Poik., median bnnd- 



r>f + hf> c-r^m nrmtnmv cnr.lT na les ' showi "g t!ie disposition of the phloem, 1, in three parts, 2, in two parts. 



Ol LlltJ hltJill dUdLUiny hUCIl db D The e ight-bnndled diagram, P. vaginatus Tuitcz. E, The four-bundled dia- 



it appearS in a CrOSS-Section g ram > F - Cheesemanil Benn. F—H, The oblong type of diagram; F, P. obtusi- 



*■ é folius M. & K.; G, P. confervoides Rchb. H, P. hicens L., 1, typical form, 2, in- 

 åt aboilt the middle Of an in- stance with a more primeval state. K—L, The circular diagram, K, P. ruti- 

 ■. f • II» l" s WoLFa. 1, from an internode at the middle of the plant; 2, from the 

 ternOQe a ieW lntemOCieS De- internode next below the primary spike, showing the spreading again of the 

 npnfh tViA nrimnrv «r»il^f> TIia lateral bundles from the median ones. L, P. foliosus Raf. showing the central 

 IlCdtll lim pilHldiy hpiKtf. Hie ste]e ]atei . all y SO mewhat compressed. All ca. *?. - »i, median bundles, /, Ia- 

 COnstituentS Of this dia°ram are tera l bundles, fb, foliar bundles, c, cauline bundles, ctr, opposite bundle, 



tr, the trio dissolved or fused to a compound bundle, sd, sclerenchyma, p, pith, 



the following parts: 1) epidei'- x, xylem canals; the chequered parts represent the phloem of the bundles; 



ct\ • , . ,1 • , , eud, endodermis. 



mis, Z) lts strengthenmg stratum 



or the subepidermal bark-layer, which rather improperly may be called hypoderma, 1 



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



1 According to the exposition of the hypoderma by some authors (for inst. E. Strassburger, Das kleine 

 bot. Pract. (1893) 66 — 67) I use this term for the stratum concerned as its chief function evidently is to 

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



