258 GRADATION OF ORGANS. Chap. IX. 



single grains are embedded iu a glutinous fluid ; in 

 all the other Orchids seen by me (except the degraded 

 Cephalanthera) the grains are united three or four 

 together,* These compound grains are tied one to 

 the other by elastic threads, but they often form 

 packets which are tied together in like manner, or 

 they are cemented into the so-called waxy masses. 

 The waxy masses graduate in the Epidendrese and 

 Vandeae from eight to four, to two, and, by the co- 

 hesion of the two, into a single mass. In some of the 

 Epidendreae we have both kinds of pollen within the 

 same anther, namely, large waxy masses, and caudicles 

 formed of elastic threads with numerous compound 

 grains adhering to them. 



I can throw no light on the nature of the cohesion 

 of the pollen in the waxy masses ; when they are 

 placed in water for three or four days, the compound 

 grains readily fall apart ; but the four grains of which 

 each is formed still firmly cohere ; so that the nature 

 of the cohesion in the two cases must be different. 

 The elastic threads by w'hich the packets of pollen are 



* In several eases I have ob- tubes are, at least at first, formed 



served four tubes emitted from exclusively at tlie expense of the 



the four grains which form one of contents of the pollen-grains, 



the compound grains. In soma Having alluded to the monstrous 



<%3mi-moiistious flowers of Malaxis flowers of the Aceras, I will add 



Ijaludosa, and of Aceras anthropo- that I examined several (always 



2)hora, and in perfect flowers of tl;e lowest on tlie spike) in which 



Neottia nidHS-avis,Iha\'e observed the labellum was hardly developed, 



tubes emitted from the pollen- and was pressed close against the 



grains, whilst still within the stigma. The mstellum was not 



anther and not in contact with developed, so that the poUinia did 



the stigma. I have thought this not possess viscid discs ; but the 



worth n>entioning as R. Brown most curious feature was, that the 



(' Linn. Transact.' vol. xvi. p. 729) two anther-cells had become, appa- 



states, apparently with some sur- rently iu consequence of the posi- 



pri.sc, that the pollen-tubes were tion of the rudimentary Itibellum, 



emitted fioni the pulluu, whilst widely separated, and wu-e joined 



Ktill within the anther, in a decay- by a connective membrane, almost 



iug flowc'r of Asclepias. These as broad as that of JJahenaria 



eases show that the protruding chlorantha .' 



