MINUTE THINGS OF LIFE. 



167 



dendron, Sigillaria, etc. They grow in great abundance, and lived 

 and died generation after generation, di'opping their cones, the 

 cones bursting and dropping the vesicles (sporangia), the sporangia 

 bursting and gi'S'ing otf the dust (spores), in the quiet and warm 

 primeval forests — grand " Wardian cases" as it were — so tran- 

 quilly, so abundantly that they accumulated thickly. Being little 

 more than hydro-carbon (the living spores will flash in a flame), 

 they have remained almost in the same state to the present day, 

 but massed as nseful seams, while the trunks and branches 

 constituted the greater part of the coal. That is, perhaps, one of 

 the most interesting and direct illustrations of minute things now 

 living, and represented also in the fossil state, that we know of. 



There is still one more vegetable matter I should like to mention 

 as very important. I have brought a specimen to remind me of it. 

 It is a little piece of sandstone (from one of the " Standing Stones" 

 of Stennis) with the Lichens that grew on it. Though very small, 

 and not growing up to rival the Fungi, yet by their coating various 

 rocks Lichens lead to the formation of soil. These tiny plants by 

 modifying the surface of rocks lead to their dissolution, and by 

 adding their little bodies to the decomposed debris of the rock, 

 actually form soil, which is washed down to a lower level, forming 

 a great part of the alluvium of valleys, and of use in various ways. 



I have given enough examples of the vegetable world, but here is 

 a limestone — it has been limestone, but is now flint — from Paris, 

 with Chara seed-vessels in it, which were called Gyrogonites before 

 it was known what they were. But they are sufficiently numerous 

 to be very important constituents in this limestone in its original 

 state. I will also hand round some engravings of the stems and 

 seed-vessels of Chara, obtained from the Scotch lakes by Sir C. 

 Lyell many years ago. These little seed-vessels and stems (as 

 above mentioned) add very considerably to some calcareous deposits. 



Now we will turn to the animal kingdom, and see what animal- 

 cula there are which have played an important part in this world. 

 We all know the common household Sponge. That particular kind 

 of sponge has not had much to do with what I am speaking 

 of. It has merely a soft horny tissue, and herein clifii'ers from other 

 sponges. Some have the same kind of tissue to a certain extent, 

 but, if you take different kinds, you will find that this fibrous or 

 network tissue has distributed in it little mineral grains, points, 

 needles, stars, etc. ; and, if you trace it from one kind to another, 

 you will find the horny tissue becoming quite mineralised, com- 

 pared with that in the bath-sponge. These particles of either silica 

 or carbonate of lime form nearly the whole of the fibre or thread of 

 the intricate network in some cases ; and they are of infinite variety. 

 Here is a sponge with some calcareous material about it, but you 

 can see that it is made up of little needle-like spicules. Here is 

 a part of another, where the spicules are star-shaped, some with 

 three arms (tri-radiate, as they are termed), and woven neatly into 

 a tissue representing just here the margin of one of the canals or 

 holes which exist in the common sponge. Here again is the surface 



