Development of Sporangia upon Fern ProthallL 255 



the cases of apogamy recorded by Stange* were of this nature, but in 

 Doodia caudata, R. Br., which is the only one of his species yet 

 investigated in detail ,f the elevations, from which sporophytes de- 

 veloped, were situated on the under surface of the prothallus. This 

 case appears to be intermediate in character between Scolopendrium 

 and the species investigated by De Bary.J 



Several prothalli were found bearing sporangia ; these were grouped 

 together in large numbers, usually upon the upper surface of the 

 cylindrical process, but sometimes both above and below. Archegonia 

 were situated close to the groups of sporangia. In the region of the 

 prothallus, underlying the group, a strand of tracheides was found ; 

 in one instance this was connected with a spherical mass of tracheides 

 developed to all appearance within the venter of an archegODium 

 whose neck had not opened. The tissue upon which the sporangia 

 are inserted is thin walled, and its cells have granular contents ; it 

 contrasts sharply with the cells of the prothallus which have a large 

 vacuole and walls which stain much more deeply with hsematoxylin. 



As in the case of Lastrcea dilatafa, the stages seen render it prob- 

 able that the sporangia follow the usual course of development. Two 

 layers of tapetal cells are formed which surround a considerable mass 

 of sporogenous tissue. Many of the sporangia fail to attain full 

 development; they remain colourless, and in time wither. A few 

 have been found, however, with a well developed annulus of a dark 

 colour; these contained spores which have not, however, been 

 examined in detail. 



In one case two ramenta overarching a group of sporangia were 

 seen. At first sight it seemed possible that they might correspond 

 to an indusium, but, when taken in connexion with another example 

 in which a cylindrical process, which bore sporangia laterally, termi- 

 nated in an apogamously produced biid, another explanation appears 

 more probable ; this will be referred to again below. 



It is worthy of note that another variety of this species has been 

 found to produce young plants, the first fronds of which bore 

 numerous prothalli while still in connexion with the stem. The 

 prothalli on which these plants appeared had been subjected to 

 repeated subdivision, a process which in other species || has been 

 found to induce apoganious development of the sporophyte. Unfor- 

 tunately nothing is known of the manner in which these peculiar 

 plants of Scolopendrium were produced, but it is possible that they 

 arose apogamously. The case of Scolopendrium would then be com- 



* ( Ber. der Gesellsch. f. Bot.,' Hamburg, 1880, p. 43. 



f Heim, ' Flora,' 1896, p. 329. 



J Loc. cit. 



In a paper by Mr. E. J. Lowe, read at the Linnean Society, February 20, 1806. 



|| Stange, loc. cit. 



