262 SUMMARY OF CURRENT RESEARCHES RELATING. TO 



conversion into fertile fronds being more or loss impeded by tho removal 

 of the barren fronds. Similar intermediate forms are also not uncommon 

 in nature, and correspond to tbo transition between barren and fertilo 

 stems in some species of Equiscfum. 



Formation of Gemmae in Trichomanes.* — Prof. F. O. Bower de- 

 scribes the formation of peculiar outgrowths on tho frond of Trichomanes 

 (datum. Tho first kind wcro ribbon-shaped prolongations of the lacinia) 

 of the frond, resembling prothallia in structure, and bearing spindle- 

 shaped gemma) seated on sterigmata. The second were long protonema- 

 like filaments widening ultimately into flat prothallium-like expansions, 

 which also bore stalked gennnse. Although no antheridia or archegonia 

 were observed, Prof. Bower believes these structures to be prothallia 

 produced by apospory. 



Enterosora.f — In his description of the plants obtained by Mr. Im 

 Thurn in his expedition in 1884 to Eoraima, British Guiana, Mr. 

 J. G. Baker describes under this name a new genus of ferns with tho 

 habit of Gymnogramme, but displaying a singular peculiarity in the 

 position of the sporangia. They are seated at the base of globular 

 chambers in the under surface of the leaf which open only by a very 

 narrow fissure, so that they are almost entirely hidden. 



Life-history of Lycopodium. % — Dr. M. Treub suggests that a more 

 natural classification than any hitherto proposed of the species of 

 Lycopodium may be based on the structure of the oophyte generation. 

 He points out that there are three distinct types of prothallium in the 

 genus, viz. : — (1) the annotinum type (not sufficiently known) ; (2) the 

 cernuum type, and (3) the Phlegmaria type. He has now studied the 

 structure of the oophyte generation in four fresh species of Lycopodium. 



In L. carinatum the prothallium appears exactly to resemble that of 

 L. Phlegmaria ; and in L. Hippuris and L. nummular! sefolium to be of the 

 same type but much larger and thicker ; while in another lycopod raised 

 from spores, probably a new species, the prothallium is of the cernuum 

 type, though differing considerably from that of that species. 



In L. cernuum the root-tops change into propagating organs of a 

 remarkable form. These root-gemma3 or bulbs produce, on germinating, 

 young plants very much like those which come forth from prothallia. 



Prothallium of Equisetum.§ — Dr. 0. Buchtien has made a careful 

 series of observations on the developmont of the prothallium of several 

 species of Equisetum, especially E. arvense, pratense, and sylvaticum. 



One of the chief points brought out in these investigations is the 

 difference in the development of the male and female prothallia. In 

 the male prothallia septa in two directions, transverse and longitudinal, 

 continue to arise, but very few lobes are formed, and, with rare ex- 

 ceptions, these always remain sterile. The first antheridium is formed 

 about four weeks after the germination of the spore. The mature 

 male prothallium is smaller than the female, and of a yellower-green 

 colour. In the female prothallium, the central portion soon becomes 

 several layers of cells in thickness, by tangential as well as transverse 

 aud longitudinal division-walls; a few cells, distinguished by their 



* Aim. of Bot., i. (1S87) pp. 1SS-4. 



t Trans. Linn. Soc. Loud.— Bot, ii. (1887) p. 294 (1 pi.). 



* Ann. of Bot., i. (1887) pp. 119-23. Cf. this Journal, 1887, p. 621. 



§ Uhlworm and Haenlein's Biblioth. Bot., Heft viii., 49 pp. and 6 pis., 1887- 



