CliYPTOGAMS 



211 



extending like arms when dry, but cnrling up suddenly 

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

 dry spores under tlie microscope 

 is gently breathed upon, it is seen 

 that the elate rs almost instantly 

 curl ; and in doing so the elaters 

 of neighboring spores become en- 

 tangled, so tliat the hitherto dust- 

 like heap becomes a coherent fluffy j^^^ps, 

 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 antheridia! pro- 

 thallia were separated, evidently 

 fertilization of the egg 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 separate description need be 

 given here. 



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

 erosporaiigiuiu of Selagiiiella only one macrospore were to mature; 

 that this macrospore were to remain permanently in the sporangium ; 

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

 the macrospore ■wall ; that the microspore should be brought to the 

 macrosporanginnr, 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 fii'st 

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

 an arrangement very like what actually exists in ovule, pollen, and 

 seed in Flowering Plants. The embr)'o 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 egg cell standing for the egg cell of an arcbe- 



A D 



Equisetum: A, a shoot 

 hearing a f ruiti ii^ cone 

 (/) ; B, axis and spo- 

 ropliylls of tlie cone ; 

 C, sectional view of a 

 sporophyll ; />, a spore. 



