168 



J. O. HAG3TROM, CRITICAL EESEARCHES ON THE POTAMOGETONS. 



Stem terete, its epidermis lacking a pseudo-hypoderma but with numerous, rather 

 strong, mechanic strands. Cortically and interlacunarly there are always a few 

 (3—6) vascular and bast bundles. Central stele of roundish crosscut-form and with 

 8 free bundles encompassed by strong, more or less open bast-sheaths. The arrange- 

 ment of the bundles becomes apparent by the diagram above. The median bundles are 

 merely two as in P. tricarinatus (eight-bimdled type). The lacunar system is the 

 usual: 3 — 4 circles of lacunae, the outer relatively large, the inner ones narrower. 



Distribution. Australia. The label bears only this annotation: — Nov. Hol- 

 land, meridional. Plantse Miillerianae. (Hb. Lund.). 



P. SpoliatllS n. sp. — Fig. 85. 



Caulis 0,5 m altus et ultra, teres 

 subcrassus simplex, internodiis 3 — 6 cm 

 longis, ramo uno prolongatus. Folia 

 superiora coriacea lanceolata vel ovali- 

 lanceolata, mucrone obtuso, 15 — 18-ner- 

 via, 40 — 60 X ± 20 mm, late petiolata, 

 petiolis foliorum floralium ca. 30 mm 

 longis. Liguloi basi subcostatae membra- 

 nacese cifco putrescentes, summse 40 — 45 

 mm longse. Peduncuhis sequalis 55 mm 

 longus. Spica densa multiflora, deflo- 

 rata 35 mm longa. Pistillum stylo 

 elongate stigmate oblongo. 



This species is characterized by the 

 short-petioled upper leaves, very soon 

 decaying lower leaves, and the noticeable 

 pistil (see the fig!). Already in an early stage the lower leaves fade away and the 

 plant, therefore, presents a poor and naked appearence, so much the more as it is 

 simple all up to the primary spike. In this respect it presents a great resemblance 

 with P. stenostachys Schum. which, however, has long-petioled leaves and very ample 

 sheaths, remarkable perianth leaves and a short fragile style. 



Stem-anatomy: The epidermis is strengthened by a pseudo-hypoderma and 

 scattered bast-bundles. Interlacunar bundles in the cortex in one circle always pre- 

 sent. Outer lacunae of the cortex considerably wider than the inner ones. Endo- 

 dermis of 0-cells and the central stele with eight free vascular bundles with equal 

 number of xylem canals. Bundle-trio reduced to a compound bundle with three 

 phloem parts and interjacent bast-cells. By those anatomic conditions it differs from 

 P. montevidensis, which for instance lacks both strengthening layer and subepi- 

 dermal strands. 



B, Pistil, 



Fig. 85. P. spnli(i/n^ Hagstr. A, Involucral leaf, 

 ovary a little grown out, 'y^. C, Transverse section of stem 

 ep, epidermis, hi/p, pseudo-hypoderma, sti; subepidermal strand 

 interlacunar bundle, cc. central cvlinder, ir, trio-bundle. 



