396 KEENS : BRITISH AND FOREIGN. 



can be seen discharging from the spore-cases like 

 puffs of smoke ; therefore Fern seed is said to be in- 

 visible, and to have the power of rendering persons 

 invisible. " I have the receipt of Fern seed and walk 

 invisible."* Be that as it may, each particle is by the 

 aid of the microscope seen to have definite forms vary- 

 ing in different genera, being globose, oval, or angu- 

 lar, smooth, plain, striated, or echinato, presenting 

 very beautiful microscopic objects. Although these 

 spores (see plate I.) are so small, they nevertheless are 

 endowed with an extraordinary power of retaining 

 their vitality ; and being easily wafted by currents 

 of air, readily account for the wide geographical 

 range of many species of Ferns. When naturally or 

 artificially placed under favourable conditions, the 

 spore vegetates by expanding in the form of a simple 

 oblong cell, from which other cells are successively 

 produced, ultimately forming a thin green membrane, 

 called the Prothallium, which lies nearly flat, and by 

 the aid of fine spongioles attaches itself to the surface, 

 and when arrived at full size it is of a reniform 

 cordate shape, or sometimes bilobed, or obcordate, 

 varying from about £ to \ inch in diameter, having 

 much the appearance of a small foliaceous lichen. But 

 before proceeding to describe the method of sowing 

 and rearing, it is important that the seed sower should 

 be made acquainted with the remarkable discovery 

 made, in 1848, by Count Leszczyc Suminski, that Ferns 

 possessed organs analogous to stamens and pistils of 

 flowering plants, and that these were produced on the 

 Prothallium. In the progress of growth peculiar cells. 



