202 VANDE.E. Chap. VII. 



no fissare along their lower surfaces for the protrusion 

 of the caudicles. The exterior pollen-grains are square 

 and have thicker walls than the interior grains, just as 

 in the proper male pollen ; and, w^hat is very curious, 

 each cell has its nucleus. Now, E. Brown states* that 

 in the early stages of the formation of the pollen-grains 

 of ordinary Orchids (as with other plants) a minute 

 nucleus is often visible ; so that the rudimentary pollen- 

 grains of Monachanthus apparently have retained — as 

 is so general with rudiments in the animal kingdom — 

 an embryonic character. Lastly, at the base, within 

 each flask-shaped pollen-mass, there is a little mass of 

 brown elastic tissue, — that is, a vestige of a caudicle, — 

 which runs far up the pointed end of the flask, but 

 does not (at least in some of the specimens) come to 

 the surface, and could never be attached to any part of 

 the pedicel. These rudimentary and enclosed caudicles 

 are, therefore, utterly useless. Notwithstanding the 

 small size and almost aborted condition of the female 

 pollen-masses, when they were placed by Dr. Criiger 

 within the stigma of a female plant they emitted " here 

 and there a rudimentary tube." The petals then faded 

 and the ovarium enlarged, but after a week it turned 

 yellow and finally dropped off without bringing any 

 seeds to perfection. This appears to me a very curious 

 instance of the slow and gradual manner in which 

 structures are modified ; for the female pollen-masses, 

 which can never be naturally removed or applied to 

 the stigma, still partially retain their former powers 

 and function. 



Thus every detail of structure which characterises 

 the male pollen-masses is represented in the female 

 plant in a useless condition. Such cases are familiar to 



♦ 'Transactions of the Linnean Soc* vol. xvi, p. 711. 



