104 MAIDEN-HAIR FERN. 



deeply notched on one edge, and held to the 

 ground by a cluster of root-hairs from the under 

 side. They may be found on the surface of 

 damp ground near patches of the fern, and may be 

 collected and preserved in alcohol. If a green-house 

 is accessible, prothallia may usually be obtained 

 fresh and in quantity from the surface of pots and 

 earth near which native or exotic species of Adiantum 

 are growing. If neither source yields suitable material, 

 the prothallia may be grown by sowing the spores of 

 Adiantum (to be obtained from the fruit dots on the 

 margins of the leaflets) on the surface of damp earth 

 packed smooth and kept at first under a bell-glass in a 

 good light. 1 Strasburger 3 recommends sowing the 

 spores on the surface of a piece of pressed peat (pre- 

 viously boiled in water to destroy other spores) which 

 is to be kept saturated with a nutritive solution pre- 

 pared according to the formula given on page 34. The 

 peat should be covered by a bell-glass and placed near 

 a north window. If prothallia of Adiantum can not be 

 obtained, the prothallia of almost any fern will show 

 the characteristic features of this stage. 



It will be advisable before attempting to cut sections 

 of the rhizome to soak it for a few minutes in water in 

 order to soften the tissues somewhat, for when taken 

 from alcohol they are extremely hard. Care will have 

 to be exercised in cutting these sections not to nick the 

 edge of the razor ; it will need frequent sharpening. 

 Before cutting the sections, the end from which they 

 are to be cut should be smoothed with a knife. 



1 Cf. Campbell, Bot. Gazette, x, p. 356. 



2 Das botanische Practicum, p. 457. 



