Thomas. — On the Prothallium of Phylloglossum. 405 



down the side of the prothallium, and the embryo appears as 

 a short cylindrical body, bluntly pointed at both ends, placed 

 vertically, and still connected with the prothallium by the 

 foot, which now has a lateral position. The ends of the 

 embryo grow downwards and upwards respectively, and at a 

 later stage what is ready the apex of the stem appears inside 

 the lower part of the embryo — that is, the embryo im- 

 mediately on escaping from the prothallium forms a proto- 

 corm, apparently in the same manner that the adult plant 

 forms its annual tuber. The pedicel of the tuber elongates 

 downwards until the latter is placed at a safe depth, about 

 3 mm., in the soil. In the meantime the leaf grows up and 

 attains a height of 2 mm. to 5 mm. above the ground. I have 

 not hitherto seen any formation of root during the first year 

 of growth, the sporophyte seemingly depending largely for its 

 supply of moisture upon the prothallium, which sometimes 

 retains its vitality even after its crown becomes injured by 

 drought. But sometimes, at any rate, rhizoids may be de- 

 veloped on the pedicel and protocorm. The leaf becomes 

 green even before it escapes from the prothallium, and as 

 soon as it reaches a little above the soil stomata are formed, 

 and air passes into the intercellular spaces, whilst a slender 

 strand of tracheids appears in the centre. The first proto- 

 phyll has, in fact, exactly the structure of a small leaf as 

 produced in later years. The further development of the 

 sporophyte appears to be slow. By carefully dissecting out 

 the plants in the soil one can find the remains of tubers and 

 roots produced in former years. In many cases the plant 

 comes up a second and a third year with only a single leaf. 



It should be mentioned here that Crie has stated that he 

 sowed the spores of Phylloglossum and obtained a colourless 

 prothallium like that of Ophioglossum. But his statements 

 have not been accepted, and recent writers, as Vines, Bower, 

 Campbell, Goebel, Pritzel,* distinctly state that the develop- 

 ment of Phylloglossum is not known. I have not had access 

 to Crie's original account, and Bertrand,f who quotes Crie's 

 statements, was unable to obtain a germination of the spores 

 during six years' experiments. But in any case it is clear 

 that Crie's account was incomplete, for the prothallium 

 becomes green, and even vividly green. According to Bert- 

 rand, Crie can only have seen the tubercle which precedes 

 the prothallium proper. 



It is not improbable that the prothallium may start life as 

 a saprophyte, aided by the endophytic fungus, and I have 



* E.g., Goebel, " Organograpbie der Pflanzen," 2te Teil, 1900, p. 439. 

 Pritzel, -in Engler and Prantl "Die Naturlicben Fflanzen-familien," 

 Lief. 205 (1900), p. 575. 



f " Archives Botaniques du Nord de la France," 1886, p. 221. 



