1882.] the Pollinium in Asclepias. 293 



cells in which no pollen-grains are developed." A very slight 

 examination will easily afford convincing proof that both of these 

 views are at variance with the facts. 



No other observer with the exception of Payer has attempted 

 to fathom the mode of origin of this membrane, and this observer 

 held that the viscid gum forming the "appendages" or "processes" 

 of the stigmatic corpusculum, which he believed was a liquid 

 secreted by a gland (the corpusculum) flowing in lateral channels 

 or grooves, when it arrived at the anther-lobes on which the 

 lateral grooves abut, penetrated into the interior of these lobes 

 and agglomerated the grains of pollen, uniting them afterwards 

 through their whole extent (vide Traite $ Org ano genie comparee 

 de la Fleur, Vol. I., page 509). This latter investigator did not 

 examine the method of development of the pollinium by means 

 of sections, or it would have been clearly evident to him that the 

 investing membrane is formed and completed at a period long 

 prior to the dehiscence of the walls of anther-loculi and conse- 

 quent exposure of the pollinia. Also that the only function per- 

 formed by the corpuscular appendages, when the anther-loculi 

 have opened by dehiscence, is that of firmly attaching the 

 pollinia to their free ends ; the substance of the two bodies 

 though externally united being never confounded, but always 

 remaining completely distinct, and moreover giving different 

 reactions with micro-chemical reagents. Schacht believed, on 

 what evidence he does not state, that the investing membrane 

 was "of the nature of a secretion," and this is the view held by 

 Prof. Oliver 1 : but such is certainly not the case ; and Dr Maxwell 

 T. Masters in his Article "Asclepiadeae," (in Lindley and Moore's 

 Treasury of Botany) hazards the statement that it is derived 

 "from the separable inner lining of the anther-cell," probably 

 referring to Brongniart's view above cited. 



It is at once obvious that the pollen-grains which are sub- 

 sequently formed in the special-mother-cells so enclosed cannot 

 be dispersed in the ordinary way, nor can the pollinia fall out of 

 the open anthers spontaneously, but remain seated there so that 

 pollination without foreign aid is impossible; and moreover the 

 flower is so very peculiarly contrived and adapted for the visits 

 of insects in search of honey that the pollinia are by their agency 

 extracted and removed en masse from their place of origin and 

 applied by the same medium to a distant part of another flower. 



Each special-mother-cell contains within its cuticularized wall 

 a mass of protoplasmic contents which have assumed a frothy 

 condition owing to the presence of a number of vacuoles or 

 oildrops. In this protoplasm spherical granules are to be met 



1 Lessons in Elementary Botany, p. 216. 



