328 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and Helminfhosiachys zeylanica, a preliminary account of which has 

 already been published in the Proceedings of the Royal Society. He 

 also describes the morphology and anatomy of the young sporophyte 

 of the latter. The young plant remains attached to the prothallus 

 until several leaves are formed ; the first leaf has a ternate lamina and 

 reaches the light. For a time a single root is developed below each 

 leaf. The first root is triarch ; succeeding ones tetrarch. A mycorhizal 

 fungus is present in a medio-cortical zone of the first few roots. The 

 stele of the stem is at first oularch and may be solid or have a small 

 pith ; it is surrounded by a well-marked endodermis. The first leaf- 

 traces are endarch or mesarch, and do not leave definite leaf-gap?. 



The author also discusses the affinity of the OphioglossacesB. The 

 form of the prothallus, structure of the sexual organs and embryogeny 

 are such as might be expected in saprophytic forms derived from pro- 

 thalli of the general type found in the Filicales. On the other hand, 

 there is little to suggest any close affinity between Ophioglossacege and 

 the Equisetales. The evidence available points to the origin of the 

 type of prothallus from forms not unlike the garnetophyte of existing 

 Marattiaccse, though possibly belonging to a more primitive group. 

 This is little or nothing to indicate an origin from the type of prothallus 

 found in the homosporous Lycopodiales. 



Classification of Ferns.* — • L. M. Underwood, in continuing his 

 notices of American Ferns, discusses the Aspidieaa, and blames the dif- 

 ferent schools of systematists for insisting exclusively on this or that set 

 of characters as of primary importance in the classification of groups of 

 ferns. He classes the values of the plant-characters of the Aspidieae 

 in the following order : — (1) venation ; (2) habit, and growth-characters 

 of stem ; (3) position of sori in relation to veins ; (4) character of in- 

 dusium. He devotes by far the greater part of the paper to a rigorous 

 examination of the validity of the generic names in the light of modern 

 rules of nomenclature. In classing the Aspidioid genera according to 

 our present knowledge, he is compelled to reduce to synonymy two such 

 well-known names as Neplirodium and Aspidium, and to replace them by 

 the older names Dryopteris and Tectaria, and he exposes the careless- 

 ness and the bias which have led authors to muddle the nomenclature of 

 the group so much in the past. He gives a key to twenty genera. 



Anatomy of Ceratopteris thalictroides. f — S. O. Ford describes 

 the anatomy of this fern, which is an annual aquatic plant, rooting in 

 the mud, or floating freely in deeper water. It is widely distributed 

 through the tropics. The much reduced stem bears both fertile and 

 sterile leaves. At the apex of the stem is a three-sided apical cell. 

 The young stem is monostelic ; at a later stage there are two steles, and 

 further division gives rise to the polystelic condition of the mature stem. 

 The steles in both stem and leaves are bi-collateral ; the former con- 

 tains an outer circle of large steles, within which small, feebly developed 

 steles are scattered irregularly. Vegetative buds are formed in large 

 numbers; they arise at the angle of a leaf, and grow by a three-sided 

 apical cell ; they are borne by both sterile and fertile leaves. The 



* Bulk Torrey Bot. Club, xxix. (1902) pp. 121-36. 

 t Ann. Bot., xvi. (1902) pp. 95-121 (1 pi.). 



