CHAPTER XVIII 



GENERAL CHARACTERS OF CRYPTOGAMS 



Essential Characteristics. — The essential characteristic of the flower, 

 distinguishing it from all other similar reproductive structures, is its 

 possession of a special tissue which constitutes a soil in which the 

 microspore germinates, and in which the male gametophyte develops 

 and grows. Plants destitute of such an organ are therefore known as 

 Flowerless Plants. An equally great or even greater distinction is 

 found in the fact that the embryo of such plants, resulting from the 

 conjunction of the male and female gametes, is not located in a resting 

 body (the seed), but must continue its uninterrupted development into 

 the sporophyte. They are, therefore, often designated as Seedless Plants. 

 Flowerless or seedless plants are technically known as cryptogams. 



Alternation of Generations. — Our account of the development and 

 reproduction of Phanerogams has shown that each individual passes 

 alternately through two different forms of life, each of which is repre- 

 sented by its characteristic body form. Those plants which present 

 themselves conspicuously to view as trees, shrubs, and herbs are sporo- 

 phytes, producing spores in ovules and anther cells, these spores ger- 

 minating to produce respectively the male and female gametophytes, 

 which constitute the other form of the plant body, or the alternating 

 generation, and which are too minute to be sfeen with the naked eye. 

 The sexual elements borne upon these gametophytic plants unite to 

 produce an embryo which is the young body of a new sporophytic 

 generation, and which is enclosed in the seed. Such an alternation of 

 generations occurs also among Cryptogams. In some cases the incon- 

 spicuous generation is the gametophyte (Fig. 599), as in Phanerogams; 

 in other cases the relations are reversed in this regard (Fig. 596). 

 Among many of the lower forms this process does not occur, each plant 

 always reproducing to form a body exactly like itself, with no indica- 

 tion of generations presenting distinct forms. 



The Cryptogamous Plant-body. — Great as are the differences seen 

 among Phanerogams, even greater ones are to be seen among those of 

 Cryptogams. They frequently present themselves as herbs, shrubs 

 and trees, with well-developed leaves, borne* upon regularly occurring 

 phytomers. In other cases, the stem-structure is well developed, while 



