226 PRACTICAL BOTANY. 



smooth inner coats of the spore, which inclose a 

 protoplasmic body with a well-marked nucleus. 



Scatter fresh spores upon a slide, and breathe upon 

 them gently ; then observe them under the microscope : 

 the elaters will be seen to execute active movements, 

 thus showing that they are hygroscopic. 



By cutting transverse sections of spikes of various stages of 

 development, which have been hardened in alcohol, or in picric 

 acid and then in alcohol, mounting them in glycerine, and com- 

 paring them, the history of the development of the sporangium 

 may be traced. The chief points to be observed will be (1) that 

 the sporangia appear as multicellular protuberances. (2) A 

 single hypodermal cell, the archesporium, gives rise by division 

 to the spore-mother-cells, while the superficial layer of cells 

 which covers the archesporium divides into three, of which the 

 outermost alone remains as the wall of the mature sporangium. 

 (3) Each of the spore-mother-cells divides into four cells, which 

 develop further into mature spores. 



THE OOPHORE. 



The fresh spores may be sown on moist soil, and the first stages 

 of germination, which are rapid, may be easily observed ; the 

 later stages are, however, slow, and to see these the cultures must 

 be carefully kept. The result is the formation of prothalli 

 (oophores) of irregular form, some of which produce antheridia 

 after five to six weeks. Other prothalli of larger size produce 

 archegonia after about two to three months. The antheridia 

 are embedded in the tissue of the prothallus, and produce large 

 antherozoids. The archegonia are borne on the upper surface. 

 The result of fertilisation of the egg- cell of the archegonium is the 

 formation of an embryo, which develops as the spore-bearing 

 plant or sporophore. 



Endeavours should be made to obtain healthy cultures of the 

 prothalli of Equisetum in which the above and other points 

 described in other Text-books may be observed. 



END OF PART I. 





