STRUCTURE.] HAVE NO SEEDS. 91 



" The analogy between the spore and the grain of pollen 

 has long been remarked ; and its extended application to the 

 processes, constituting germination in the one instance, and 

 the formation of the seed in the other, was given by 

 Mr. Valentine in 1833. I think I am correct in naming it 

 analogy rather than affinity, from considerations derived both 

 from development and functional powers. For the spore of 

 these particular or more developed Acotyledons is not pro- 

 duced by a comparatively simple process as the pollen of 

 Cotyledonous plants is, but is the result of a process as 

 complicated, if not more so, than the development of the 

 seed, and, in addition, presents in its first stages very curious 

 similarities with the development of a true ovulum. Both 

 agree in being set in action by the agency of a comparatively 

 simple structure ; but the early complication of the process in 

 the higher Acotyledonous plants would at once lead me to 

 suspect that the organs alluded to are not strictly similar ; for 

 the earlier we proceed in our investigations, the more marked 

 should be the resemblance, and the more simple both struc- 

 ture and function. The powers of growth in the two are 

 remarkably contrasted, and will be still more so, if the albu- 

 men be ultimately found to be derived from the female. 

 M. Schleiden, on the contrary, is of opinion, that between 

 the spore and the embryo there is an affinity amounting to 

 fundamental unity; and Mr. Valentine not only holds the 

 same opinion, but, overlooking the obvious difficulties to 

 which M. Schleiden has adverted as presented by some of 

 the higher Cryptogamic families, denies to these plants 

 entirely a provision similar to that of the pistillum of Pha- 

 nerogams." (Linn. Trans., vol. xix.) 



How little analogy there really is between the spores of 

 some flowerless plants and the seeds of the higher orders is 

 sufficiently shown by the following excellent account of the 

 formation of that of Vesiculifera concatenata, an Algal, 

 by Mr. Thwaites : 



" This plant occurs in ponds on a common near Bristol, 

 and is of a pleasant pale apple-green colour. The cells are 

 usually from five to seven times as long as broad, and are 

 lined with but a small quantity of endochrome, which is 



