90 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the Hymenophyllaceee and that of Mosses. He regards the primitive 

 form of both to be a filiform protonema bearing directly sexual organs 

 of both kinds ; the original function of the leaves being simply to serve 

 as a protecting envelope. The Hymcnophyllaceaj would therefore be 

 the archaic type of Ferns. 



Dehiscence of the Sporangium of Ferns.*— Miss F. M. Lyon 

 describes the dehiscence of the sporangium of Adiantum pedatum as 

 always taking place along a definite line across the side of the sporangium. 

 This line is always determined by the presence of two narrow and 

 elongated cells with lignified walls opposite the annulus and about mid- 

 way between its end and the stalk, between which the fissure commences. 

 These " lip-cells," the occurrence of Avhich appears hitherto to have been 

 overlooked, were observed also in a number of other species. The 

 authoress suggests that their presence may have an important bearing 

 on the causes which produce the dehiscence. 



Heterophyllous Ferns. - ! - — Herr K. Goebel points out that the usual 

 statement that in the heterophyllous species of Polypodium (P. Willde- 

 nowii, rigidulum, and quercifoliunx), one form of frond is sterile and the 

 other fertile, is incorrect ; both forms being fertile. The so-called fertile 

 fronds are pinnatifid, long-stalked, and deep-green, and very soon die 

 down to the rachis ; the " sterile " fronds, on the other hand, are sessile, 

 cordate, and convex below, so as to form an open " niche " above ; they 

 very soon lose their green colour, and wither away with the exception of 

 a framework formed of the veins. The purpose of these leaves appears 

 to be the collectien of humus into which the roots of the fern penetrate, 

 thus enabling them to obtain nutriment where otherwise it would be 

 impossible. In Polypodium Heracleum, both functions, assimilation and 

 the accumulation of humus, are performed by the same fronds, all having 

 the same form with strongly dorsiventral structure ; the base of the leaf 

 forms the " niche," the ribs of the frond the framework for the collection 

 of humus. Leaves of the same kind occur in some epiphytic orchids, as 

 Bolbophyllum Beccarii. 



The same explanation is offered of the heterophylly of the " elk's- 

 horn fern," Platycerium grande and alcicorne. The branched fronds 

 serve for the purpose of assimilation, while the intermediate, sessile, 

 unbranched, reniform fronds serve both to retain moisture, and to 

 accumulate humus. At the base of these leaves is a strongly developed 

 aquiferous tissue. Many epiphytic ferns, such as Drymoglossum, have 

 similar receptacles for water. In Polypodium sinuosum and patelliferttm, 

 the hollow stem serves as an abode for ants ; and the same is the case 

 with the hollow pseudobulbs of some orchids. Organs of secretion occur 

 in both kinds of fronds of P. quercifolium. 



Characeae. 



New Species of Characese4 — Dr. T. F. Allen describes and figures 

 the following new species : — Nitella Muthnatse from Muthnata Island in 

 the Feejee group ; Tolypella Macounii from Niagara river, and Nitella 

 Morongii from Nantucket. The Tolypella is especially noteworthy from 



* Bull. Torrey Bot. Club, xiv. (1887) pp. 180-3 (4 fig?.). 



t Ann. Jard. Bot. Buitenzorg, vii. (1887) pp. 1-21 (1 pi.). See Bot. Centralbl., 

 xxxii. (1887) p. 165. 



% Bull. Torrey Bot. Club, xiv. (18S7) pp. 211-5 (5 pis.). 



