The  3rd paragraph on p. 441 is actually correct.

Basically, spores are always haploid and never need to fuse with another spore. Gametes, on the other hand, are haploid but do need to be fertilized (fuse with another opposite gamete). 

Here is a synopsis that might help: Alternation of generation in plants (mosses, ferns, gymnosperms, and angiosperms) involves a haploid gametophyte that produces haploid gametes. The haploid sperm fertilizes the haploid egg to produce a diploid zygote that develops into a diploid sporophyte. (This is the plant.) The diploid sporophyte produces haploid spores through meiosis. These haploid spores undergo mitosis (process of duplication) and directly develop into a new plant gametophyte (which is haploid) without needing another spore.

It may be confusing because in gymnosperms and angiosperms, the gametophytes are small parts of the whole plant. In mosses and ferns they are larger and more visible. The paragraph on page 441 that talks about this is referring to all four of the major plant groups.  If you add the word gametophyte after the word plant in this sentence of the third paragraph, it should clarify that.  "Remember that, like spores of fungi, haploid spores of plants can develop into a new plant gametophyte without fusing with another spore."