208 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The foliar traces of the Filicineaa clearly exhibit their special cha- 

 racters only in sufficiently strong leaves. The greatest complication of 

 the foliar trace is found in the petiole. In the great majority of living 

 FilicinesB the fibrovascular chains of the foliar trace usually form a 

 single curve. The special characteristics of the foliar trace are de- 

 scribed in Osmunda, in the Cyatheaceae, in the Ophioglossacese, and in 

 some genera of Polypodiaceaa. By means of the foliar trace the funda- 

 mental tissue of the petiole may be seen to consist of an external funda- 

 mental tissue and an internal fundamental tissue, which is well defined 

 when the trace is closed. 



Type-Specimens of Lyginodendron Oldhammm.* — E. A. N. Arber 

 figures and gives descriptions of some of the original sections on which 

 Binney, in 1866, founded his account of the fossil plant Dadoxylon 

 Oldhamium, subsequently transferred by Williamson to Lyginodendron. 

 Binney did not figure any of his sections. 



Prothallium of Phylloglossum. f — A. P. W. Thomas, of Auck- 

 land, finds prothallia growing naturally among the parent plants in 

 three localities only, suggesting that special conditions are necessary 

 for the germination of the spores, conditions which are not of regular 

 annual occurrence wherever Phylloglossum grows. Perhaps the most 

 important is the presence of a fungus, with which, as in the case of the 

 prothallia of Lycopodium, that of Phylloglossum lives symbiotically. 

 The prothallium varies much in external form. In the youngest stage 

 observed it consisted of an oval tuber from which rises a simple cylin- 

 drical shaft with a rounded apex. The tuber, which is of constant 

 occurrence, doubtless corresponds with the primary tubercle in the pro- 

 thallium of Lycopodium cernuum. The shaft varies considerably in 

 length and thickness, and may be straight or curved, the whole pro- 

 thallium varying from less than 2 mm. in length to thrice this. Rhizoids 

 are numerous on the lower part, especially on the tubercle. The shaft 

 expands above into a crown, which may be conical, rounded, or project- 

 ing to one side, and bears the sexual organs. The whole upper part of 

 the prothallium is green, except the projecting necks of the archegonia ; 

 the green colour passes away as the shaft enters the ground. Sections 

 show little internal differentiation of the prothallia ; an endophytic 

 fungus may be traced in the cells of the lower half, the hyphae ma*.- be 

 seen passing in through the rhizoids. The fungus forms a close felt 

 around the tubercle, passing below it into a root-like strand. The 

 archegonia, which reach from ten to twenty in number, appear to be 

 formed in basipetal succession, the neck projects as a hemisphere of 

 colourless cells, usually in two tiers of four cells each. The venter, 

 with the large oosphere, lies at a little depth below the surface. The 

 antheridia form an elongated cavity with a single layer of cover- cells. 

 The sexual organs resemble most those of Lycopodium cernuum ; there 

 are no paraphyses as in L. Selago and L. PMegmaria. 



The development of the embryo at first resembles that of L. cernuum. 

 It first grows obliquely downwards and outwards; the part near the 

 venter is the foot ; at the opposite end are formed the stem-apex and 



* Proc. Camb. Phil. Soc, xi. (1902) pp. 281-5 (2 figs.), 

 t Proc. Roy. Soc, lxix. (1902) pp. 285-91. 



