78 



143. POLYSTACHYA luteola. 



Hooker Exotic Flora, t. 105. 



P. luteola ; caulescens, foliis oblongo-lanceolatis, panicula racemosa ramis ab- 

 breviatis, floribus glabris, sepalorum basi triangulari, labelli lobo medio sub- 

 cuneato apiculato disco furfuraoeo, capsula inter costas subavenia.= 

 Dendrobium polystachyon Swartz. 



The plant figured by Sir W. Hooker is certainly that 

 from the West Indies ; and there must have been some mis- 

 take in the Liverpool Garden, where it was said to have been 

 received from Dr. Wallich from the East Indies. It does not 

 appear among any of Dr. Wallich's collections, and probably 

 was never in his possession. 



144. POLYSTACHYA zeylanica. 



P. zeylanica ; caulescens, foliis oblongo-lanceolatis, panicula racemosa ramis 

 elongatis, floribus glabris, sepalorum basi triangulari, labelli lobo medio 

 rotundato apiculato disco furfuraceo in medio nudo calloso, capsula inter 

 costas reticulata. — Dendrobui?n polystachyum Tbouars Orch. Afr. t. 85. 



In both these plants the disk of the labellum is covered 

 with a fine frost-like mealiness, which is removed by the 

 least touch. This mealiness is a curious modification of the 

 hairs found in other plants. When undisturbed it consists 

 of threads with egg-shaped joints, which are filled with air ; 

 the surface of each joint is marked with wavy oblique striae, 

 and the interior uniformly contains a nucleus, to which there 

 appears to belong a circulating apparatus of the same nature 

 as that in the hairs of Tradescantia and other plants ; I have 

 not however succeeded in actually observing any circulation. 

 But the slightest touch suffices to destroy the cohesion be- 

 tween the joints of these singular necklace-shaped bodies, so 

 that when they are placed on the field of the microscope the 

 latter appears as if covered with the eggs of some insect ; it 

 is only when they are removed from the labellum with great 

 care that their real articulated structure, and their analogy 

 with such hairs as those of Tradescantia, is made out. 



