Holloway. — Tin Prothallus and Young Plant of Tmesipteris. 11 



but in the latter was apparently quite complete. The prothallus shown 

 in fig. 4a tapered off at the basal end to a single cell, which showed 

 no sign of original farther extension such as would compare with the 

 longer filament in figs. 1a and 11. But the single cell in which the 

 basal point of most of the youngest prothalli found by me terminated 

 did give evidence of having had a farther cellular extension broken away 

 from it, In all these prothalli the terminal basal cells, whether single or 

 in the form of a short linear filament, all contained the same dense masses 

 of the fungal element which are present in the other parts of the prothallus. 

 Thus it would seem that the 

 fungus enters the prothallus im- 

 mediately the spore begins to 

 germinate, unless perhaps we 

 take it that it spreads downwards 

 into the filament subsequent to 

 the infection of the prothallus 

 through the first-formed rhizoids. 

 Probably the delicate original 

 basal filament owes its preserva- 

 tion to the fact of the presence in 

 its cells of these fungal masses, 

 the collapse of the cells being 

 thus prevented. At any rate, 

 the preservation of the actual 

 original point of the prothallus 

 of Tmesipteris in so many indi- 

 viduals, some of which were well 

 grown, is rather remarkable. It 

 would seem, then, though it must 

 be stated that the remains of the 

 originating spore itself have not 

 been seen, that on germination 

 the spore gives rise to a short 

 linear filament of cells, and that 

 this, after from one to three or 

 more single cells have been cut 

 off, proceeds to the formation of 

 a cell-mass. This basal primary 

 tubercle is well preserved in the 

 prothalli shown in figs. 1, 2, 4, 

 11, 12, and 13, and it will be seen 



that in most cases it shows no great development. The further stages of 

 growth of the prothallus can be clearly seen from a comparison of the 

 young and the older individuals shown in these figures. The prothallus 

 grows in a succession of gentle swellings, each a little bigger than the last, 

 the increased cell-multiplication which these swellings indicate being due 

 probably to the accumulation of food material at the apex, consequent 

 on the activity of the mycorhiza. In fig. 14 is shown one of the limbs 

 of the large prothallus illustrated in fig. 6 ; serial sections through this 

 limb showed that the cells of the apical region were packed with starch. 

 Thus, as the prothallus grows, its apex becomes more and more bulky, so 

 that the whole prothallus-body acquires the carrot form, until at length, 

 owing probably to the stimulation set up by the presence of abundant 



Fig. 12. — Very young complete prothallus, 

 showing papillose -like outgrowth of epi- 

 dermal cells. Antheridia on head. X 45. 



