262 LINES OF DESCENT. CiiAi' IX 



the caudicle is actually more than thrice as louff as the 

 elongated pollen-masses ; and it is highly improbable 

 that so lengthy a mass of grains, slightly cohering 

 together by the aid of elastic threads, should ever have 

 existed, as an insect could not have safely transported 

 and applied a mass of this shape and size to the 

 stigma of another flower. 



We have hitherto considered gradations in the state 

 of the same organ. To any one with more knowledge 

 than I possess, it would be an interesting subject to 

 trace the gradations between tlie several species and 

 groups of species in this great and closely-connected 

 . order. But to make a perfect gradation, all the extinct 

 forms w^hich have ever existed, along many lines of 

 descent converging to the common progenitor of the 

 group, would have to be called back into life. It is 

 due to their absence, and to the consequent wide gaps 

 in the series, that we are enabled to divide the exist- 

 ing species into definable groups, such as genera, 

 families, and tribes. If there had been no extinction, 

 there would still have been great lines or branches of 

 special development, — the Yandeae, for instance, would 

 still have been distinguishable as a great body, from 

 the great body of the Ophreoe ; but ancient and inter- 

 mediate forms, very different probably from their 

 present descendants, would have rendered it utterly 

 impossible to separate by distinct characters the one 

 great body from the other. 



I will venture on only a few more remarks. Cypri- 

 pedium, in having three stigmas developed, and there- 

 fore in not possessing a rostellum, in having two fertile 

 anthers with a large rudiment of a third, and in the 

 state of its pollen, seems a remnant of the order whilst 

 in a simpler or more generalised condition. Apostasia 



