518 Minnesota Plant Life. 



flowering plants and insects, have come to be highly developed 

 as a partnership, constituting, indeed, the most remarkable 

 association of all those existing between plants and animals. 



Germination of spores. When a spore enters upon the course 

 of development through which a new plant comes into exist- 

 ence, it is said to germinate. Perhaps not quite all the cell 

 divisions that are undergone by spores should be classed as 

 germination-stages. In lichen-fungi, for instance, and in many 

 others, spore-cells before they are separated from the parent 

 plant divide once or more, even building considerable aggre- 

 gates; but this behavior seems rather a multiplication of the 

 spore-cells than true germination. Yet even among distrib- 

 uted spores germination sometimes begins before the spore 

 leaves the body of its parent. This is true of the cone-headed 

 liverwort, the spores of which become . divided into internal 

 compartments before they are scattered from their capsule. 

 Such division seems to constitute a true germination, for later 

 divisions, by which the liverwort first-stage plant is constructed, 

 follow in unbroken sequence, after the spore wall has been 

 fractured. Undistributed spores, such as embryo-sacs, ger- 

 minate at the spot where they were produced. 



If the outer wall of the spore is hard and brittle, as is usually 

 the case, it must be broken by the expansion of its contents 

 unless the sporeling is destined to remain principally or en- 

 tirely within the confines of the spore. The latter condition 

 actually obtains among many large-spores and is notably char- 

 acteristic of the embryo-sacs of flowering plants. In them the 

 female matures and produces her eggs without ever leaving 

 the spore from which she arose. And in smaller club-mosses, 

 quillworts and four-leafed water-ferns the male matures within 

 the small-spore, the wall of which is finally broken open to 

 liberate the spermatozoids. In all such instances the sporeling 

 nourishes upon substances present in the spore and does no 

 independent vegetative work. If, however, the sporeling is 

 destined to gather nutriment from the outer world it very early 

 establishes itself as a filament, plate or mass of cells, breaking 

 or dissolving the original spore wall in the process. Thus, fern 

 spores, when ejected from their capsules upon a sufficiently 

 moist surface, soon crack open and a transparent-walled cell is 



