174 



J. O. HAGSTROM, CEITICAL RESEARCHES ON THE POTAMOGETOXS. 



The fruit of specimens from Takapo Lake is obliquely obovate, with a short beak 

 and faint dorsal keel, scarcely 2 mm long by 1,3 mm broad. — Genuine submersed 

 leaves, when occurring, rounded obtuse or slightly emarginate in the apex, nerved 

 as is shown in the fig. below. Midrib lacunous, the two chief lateral nerves running 

 nearer to the margin than to the midrib. Leaf-base narrow and a little sloping; 

 petiole at least in the lower leaves very short or inconspicuous. 



The epidermis of the stem, consisting of somewhat stretched cells, always lacks 

 strengthening layer. Endodermis composed by Ocells with a very faint tendency 



a to one-sided thickening. The cortical 



bast or vascular bundles now spread 



toward the epidermis, now appear 



between the utmost lacunar circle 



and the next to it. The central 



cylinder is characterized by the two 



great median bundles with inter- 



jacent compact mechanic tissue. 



The lateral bundles are usually re- 



duced in number, more rarely 2—3 on 



either side (shallow-water form from 



Hokianga, below! and pp. 169, 176!). 



The length of the peduncles and 



the upper internodes varies consider- 



ably. In the main-form, of St. 



John's Lake, the petioles of the 



primary involucral leaves are of 



cciual length to the blades and those 



of the leaves next below likewise 



comparatively short. Specimens from 



Nelson (see below!) ha ve rather 



elongate internodes (10 — 17 cm) next below the primary spike and the petioles of 



the primary involucral leave likewise elongate (9 — 10 cm). I have called such specimens: 



f. corymboides n. f. — F. foliis flor. prim. longissime petiolatis, internodiis 



supcrioribus valde elongatis. — 



The specimens from Hokianga evidently are a shallow-water form with a couplc 

 of branches at the base, short internodes and only coriaceous leaves: 

 t. Erondosus n. f. — F. foliis onmibus coriaceis v. subcoriaceis. — 

 The specimens from Tasmania, again, have sessile or very short- pctioled sub- 

 meraed Leaves and reduoed faculty of developing coriaceous leaves. Ucsidcs, this 

 form entirely lacks the interlacunar circle of bundles, whereas the subepiderinal onc 

 is wcll supplied. This plant I name: 



f. (asinaniciis n. f. — Folia subinersa scssilia vcl in superiore parte caulis biv\ i- 

 petiolata, omnia obtusa, baei lanoeolata; natantia Bero evoluta parva ovalia. — 

 Fig. 91, A'— 11. 



Fig. 91. 



/'. Cheesemanii Benn. A — 1>, typical form. A, Involucral 

 leaf, j ll. Top of ;i Milnnersod leaf, ; (from Lako Pearson). C, Pistil, 

 sideview, '^ (from st. Johns Lake). D, Transverse Bectton of tlio stele, 

 a — «, median bundles; b, bast; '■, lateral bundles, ',". — E — 11, form 

 tiumanieus Haostb, /.', Involncral leaf, J. >', Top of a submersed leaf, 

 J. G, 1'istil, lateral \ i< •»• << , from above (b), ','• H, Diagrammatio cross- 

 sc-tiuii ol the stem, Bhowing the central stele (identic with that of tho 

 typ. form) and the >ubei)idermal strands, -',". 



