80 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Investigations on Fern-Prothallia.* — A. Jakowatz has studied the 

 development of the prothallium in several members of Polypodiaceae T 

 and finds remarkable differences in the early stages of development 

 and their conversion into the later flat expanded form. It is, however, 

 impossible to say whether these differences are characteristic of the 

 various species or genera. In some species the developmental course 

 in these stages follows a definite scheme ; in others, different types of 

 development are observed apparently without reference to external 

 conditions. There is, however, a common law governing the first stages 

 of development, which in all the forms investigated begins with a 

 thread-like stage ; the growth of this becomes closed, while the flat pro- 

 thallial growth originates from an apical cell appearing laterally on the 

 filiform rudiment. Often the formation of a branch coincides with the 

 formation of this cell, which then comes to stand in the axil of the 

 branch. The further development of the pro thallial surface depends 

 on the well-known segmentation of the apical cell. The segments, 

 always the earliest, show a limited growth and often conclude with a 

 papilliform terminal cell. 



In the filiform rudiment, the lateral origin of the later flat structure, 

 and the formation of segments with limited growth, the ferns investi- 

 gated show a remarkable homology with the development of the mosses. 

 We may regard the thread-like rudiment as a protonema stage, and the 

 papilla-like ends of the segments as structures homologous with the 

 leaf -ends of the Muscineae. 



Tropical American Ferns. f — C. A. M. Lindman gives an account 

 of the ferns collected by him during the first Regnell Expedition 

 (1892-4) in Brazil and Paraguay, and of those collected by Regnell, 

 Mosen and others, thirty to fifty years ago. In all he records 209, sixteen 

 of which, with three varieties and nine forms, are new. Having 

 examined Swartz's types at Stockholm, he has revived several old 

 species which had been misunderstood or quite forgotten. This has 

 involved change of nomenclature and synonymy. He has followed the 

 general lines of Hooker's Synopsis Filicum. Finding the old descrip- 

 tions too elastic and indefinite, he pleads that they be made more exact, 

 and hence more helpful to collectors in enabling them to appreciate rare 

 species, which run the risk of being disregarded as mere forms of 

 common species too loosely defined. 



Trichomanes (sect. Didymoglossum)4 — C. A. M. Lindman publishes 

 critical notes on the American species of Didymoglossum Desv., a section 

 of the genus Trichomanes. Having studied Swartz's little-known types 

 in the Stockholm Museum, he is able to correct the erroneous con- 

 ceptions which Hooker, Greville, and others, formed of the species 

 T. apodum, muscoides, reptans, quercifolkim, etc., and to amend the con- 

 fusion that has consequently arisen. He has carefully re-described the 

 original specimens, and, as words are insufficient to give an accurate 

 idea of such difficult plants, he has found it indispensable to add a 

 number of camera-lucida drawings to prevent future misunderstanding. 



* SB. K. Akad. Wiss. Wien, Math.-naturwiss. CI. ex. (1901) pp. 479-505(7 pis.)- 

 t Arkiv. for Botanik. Stockholm, i. (1903) pp. 187-275 (8 pis.). 

 j Tom. cit., pp. 7-56 (31 rigs, in text). 



