CRYPTOGAMS 



211 



extending like arms when dry, but curling up suddenly 

 when moistened by water or damp air. If a lot of the 

 dry spores under the microscope 

 is gently breathed upon, it is seen 

 that the elaters almost instantly 

 curl ; and in doing so the elatenii 

 of neighboring spores become en- 

 tangled, so that the hitherto dust- 

 like heap becomes a coherent fluffy 



B 



A D 



Equisetura: A, a shoot 

 bearing a fruiting cone 

 (/) ; B, axis and spo- 

 rophylls of the cone ; 

 C sectional view of a 

 sporophyll ; D. a spore. 



mass. This entanglement of the 



spores is of importance in the 



economy of the plant, from the 



fact that the prothallia to which 



they give rise are of two kinds. 



One kind bears archegonia alone, 



the other only antheridia. If 



archegonial and antheridial pro- 



tiiallia were separated, evidently n 



fertilization of the Qgg cells by 



the antherozoids could not take 



place, and new Equisetum plants 



would not be produced. The pro- 



thallium and its organs are so much like corresponding 



structures in Ferns that no sejiarate description need be 



given here. 



Relationship of Cryptogams and Phanerogams. — Suppose in the ma- 

 crosporangium of Selaginella only one macrospore were to mature ; 

 that this macrospore were to remain permanently in the sporangium ; 

 that the prothallium were to be still further reduced, so as not to burst 

 the macrospore Avail ; that the microspore should be brought to the 

 macrosporangium, and put out a tube, which, penetrating into the 

 macrospore, should conduct the antherozoids to the archegonia ; and 

 that the resulting Selaginella plant should develop and form its first 

 pair of leaves quite within the macrospore, — then we should have 

 an arrangement very like what actualh^ exists in ovule, pollen, and 

 seed in Flowering Plants. The embryo sac of Phanerogams is 

 regarded as a macrospore remaining in its sporangium (nucellus of 

 ovule, the integuments representing the indusia of some Pterido- 

 phytes). The several nuclei of the sac probably represent cells of a 

 reduced prothallium, the e^g cell standing for the egg cell of an arche- 



