Prof. Nees von Esenbeck on New Holland Plants, 45 



which in their interior contain plate-like rings and spirals 

 raised on the narrow edge, which constitute nearly the entire 

 mass of the wood of the Mammillarid', Echinocacti, and Melo- 

 cacti ; and also occur in small quantity in the Opuntia, espe- 

 cially at the contractions of the joints, and which were first 

 described by Meyen from Opuntia cylindrical 



EXPLANATION OF PLATE. 



Fig. 1. — 10. Stages of the formation of the annular vessels from Campella 



Zanonia, Rich. Explanation in text, page 42. 

 Fig. 11. Commencement of the formation into a ring of a spiral from 



Equisetum arvense. 

 Fig. 1 2. Spiroidea on a section through the medulla perpendicular to the 



bark; a. the side towards the medulla, b. that toward the bark. 

 Fig. 13. Spiroidea on a section parallel to the bark. 



Fig. 14. The same as in fig. 13, with an intermediate series of cells cor- 

 responding to a right wound spiral. 

 Fig. 12 — 14. From young stems of Cucurbit a Pepo. 



V. — Characters of new Genera and Species of New Holland 

 Cyperaceae, Restiaceae, and Juncaceae. By Prof. C. G. 

 Nees von Esenbeck. 



[Communicated by Professor Lindley.~] 



A. GUNNIAN^E. 



Helothrix. 

 Locus inter Cyperaceas Acrolepideas. 



Gen. Char. Spicula disticha, squamis duabus inferioribus minori- 

 bus sterilibus, duabus superioribus hermaphroditis. Stamina 

 tria. Perigynii setae 4 (an semper ?) retrorsum scabrae. Stylus 

 bifidus, a basi bulbosa deciduus. Caryopsis biconvexa, styli 

 basi conica mucronata perigynioque stipata. 



Inflorescentia : spiculae axillares et terminales geminae brevipedun- 

 culatae. 



Plantae pusillae habitu Jcrolepidis, Schrad. aut Eleogitonis, in inundatis 

 degentes, diffusa?. Culmus ramosus, flexuosus, foliosus. 



*974. Helothrix pusilla. Culmi 2 — 4 poll, longi, flaccidi, geniculati, 

 compressi. Vaginae internodiis breviores, totae herbaceoe, striatse 

 ore truncatee. Folia linearia, angusta, obtusa, margine scabra, 

 trinervia. Spiculae vix lin. 1. longae ex vaginis superioribus 

 emergentes, plerseque geminse, pedunculis inclusis, oblongae, 

 compressae, virides cum purpura. Squamae carinatae, duae in- 

 feriores triplo majores uninerves acutae, duae superiores ovato- 

 lanceolatae obtusae trinerves, apice virides, basi pallidae, deciduae. 

 Stylus bifidus, ramis longis tortis hirtis. Caryopsis Candida, 



* The numbers refer to the collections of dried plants given away by 

 Mr. Gunn. 



