304 MISCELLANEOUS OBJECTIONS TO THE [Chap. YIL 



the flowers of orchids, namely their pollinia. A pollinium 

 \Yhen highly developed consists of a mass of pollen-grains, 

 affixed to an elastic foot-stalk or caudicle, and this to a 

 little mass of extremely viscid matter. The pollinia are 

 by this means transported by insects from one flower 

 to the stigma of another. In some orchids there is no 

 caudicle to the pollen-masses, and the grains are merely 

 tied together by fine threads ; but as these are not con- 

 fined to orchids, they need not here be considered ; yet I 

 may mention that at the base of the orchidaceous series, 

 in Cypripedium, we can see how the threads were pro- 

 bably first developed. In other orchids the threads 

 cohere at one end of the pollen-masses ; and this forms 

 the first or nascent trace of a caudicle. That this 

 is the origin of the caudicle, even when of considerable 

 length and highly developed, we have good evidence 

 in the aborted pollen-grains which can sometimes be 

 detected embedded within the central and solid parts. 



With respect to the second chief peculiarity, namely 

 the little mass of viscid matter attached to the end of 

 the caudicle, a long series of gradations can be specified, 

 each of plain service to the plant. In most flowers 

 belonging to other orders the stigma secretes a little 

 viscid matter. Now in certain orchids similar viscid 

 matter is secreted, but in much larger quantities by one 

 alone of the three stigmas ; and this stigma, perhaps in 

 consequence of the copious secretion, is rendered sterile. 

 "When an insect visits a flower of this kind, it rubs off 

 some of the viscid matter and thus at the same time 

 drags away some of the pollen-grains. From this simple 

 condition, which differs but little from that of a multi- 

 tude of common flowers, there are endless gradations, — 

 to species in which the pollen-mass terminates. in a very 



