288 Mr. A. P. W. Thomas. 



theridial cavity is elongated at right angles to the neighbouring 

 surface. The cover cells form a single layer. The sexual organs 

 would seem to resemble those of L. cernuum more closely than 

 those of other species of Lycopodium. There are no multicellular 

 paraphyses amongst the sexual organs as in L. Selago and L. phleg- 

 maria, but on some parts of the crown the surface cells are slightly 

 papillose. 



The thickness of the tissues renders it impossible to follow the 

 details of the early development of the embryo, except in microtome 

 sections. But it seems clear from the stages which have so far 

 been examined, that the development at first is much like that of 

 the embryo in L. cernuum. ^The embryo grows obliquely downwards 

 and outwards, the part near the archegonial venter is the foot, at 

 the opposite end are formed the stem-apex and leaf. The first part 

 of the embryo to appear outside the prothallium is the tip of the leaf ; 

 it breaks out at a point on the side of the thicker part of the pro- 

 thallium, below the crown ; a fissure extends thence 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 really the apex of the stem appears inside 

 the lower part of the embryo that is, the embryo immediately on 

 escaping from the prothallium forms a protocorm, 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 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 developed 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 protophyll 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 care- 

 fully 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. j 



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, 



