28 THE LIFE OF THE PLANT 



with lightning-like flashes, an effect used in former days 

 to represent lightning on the stage. In this explosion 

 have perished in their embryonic state millions of future 

 plants. These microscopic bodies are called spores by 

 botanists, and all the plants derived from them and 

 devoid of flowers and seeds are called spore-bearing 

 plants. Beside the plants already mentioned this class 

 comprises mosses, water-weeds called green-slime in 

 everyday language, and also fungi, a group which in- 

 cludes moulds as well as mushrooms. 



Thus we notice that a spore-plant, whether micro- 

 scopic mould or tree-fern, owes its origin to an invisible 

 grain of dust — a. spore. What is this spore ? Is it not 

 the simplest starting-point of plant life, for which we 

 have been seeking and which we could not think that 

 we had found in the seed ? 



As a matter of fact microscopic investigation shows 

 that the spore consists of a bladder with a solid exterior, 

 containing within it liquid and semi-liquid matter. 

 This is the so-called cell, and it is to the cell that we 

 must look for the simplest origin of every organism ; 

 we are unable to split it into parts capable of independent 

 existence ; it marks the limit of morphological analysis ; 

 it is the organic unit. This being the case a question 

 at once occurs to us : could we not also trace a seed 

 back to a single cell, for surely it does not arise straight 

 away with its root, stem, and cotyledons ? We shall 

 have an opportunity in a subsequent lecture of proving 

 that every seedling also starts from a single cell. We 

 shall discover this cell in the ovule when we come to 

 know its structure better. Hence it follows that every 

 seed-plant or spore-plant starts its existence as a single 

 cell. The only difference between them consists in the 

 fact that in the case of the spore-bearing plant the cell 

 becomes separated from the plant which has produced 

 it ; whereas in the seed-plant the cell develops and 

 grows into a complicated organ, a seed, and only in 



