268 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The generic characters are discussed in detail ; the systematic position of 

 the senus is considered, and the phyletic relations are treated at some 

 length, followed by a technical discussion of the eleven species, seven of 

 which are new to science. The genus has a wide geological range in 

 Xorth America. A. G. 



' Archesporial and Meiotic Mitoses of Osmunda. — L. Digby (Annals 

 4)f Botany, 1919, 33, 185-72, 5 pis. and fig.)- A fully illustrated 

 account of cytological investigations of various species of Osmunda. 

 The summary of the results is far too long for citation ; but the chief 

 results are given as follows : — (1) It is shown that telophasic events 

 have an important bearing on the interpretation of the succeeding 

 prophase. (2) That the sequence of events in prophase can only be 

 interpreted in the light of the preceding telophase. (3) The above- 

 mentioned facts have been found to be of fundamental importance in 

 •elucidating the early stages of the heterotype division. (4) In the 

 heterotype division the prophasic stages, ordinarily included under 

 ■" synapsis," do not consist in the lateral conjunction ol two entire iiom^aWc 

 chromosomes, but in the lateral re-association of the threads in pairs 

 which together make a single entire somatic chromosome. (5) Conjunction 

 in pairs of entire somatic chromosomes occurs in the stages leading up 

 to, and is finally consummated during, second contraction. A. G. 



Study of Apogamy in Nephrodium hirtipes Hook. — W. N. Bteil 

 {Annals of Botany, 1919, 33, 109-32, 3 pis.). A resume of previous 

 work on apogamy, and an account of the author's own observations, 

 summarized as follows :— (1) The prothallium of Nephrodium hirtipes 

 arises from the germination of a spore. (2) The gametophyte never 

 produces archegonia ; but antheridia are formed which develop apparently 

 normal antherozoids. (3) The development of secondary prothallia is 

 readily induced by culture. (4) Attempts to induce an aposporous 

 gametophyte development have rarely been a success. (5) The embryo 

 originates at an early stage in the development of the gametophyte as a 

 vegetative outgrowth of the prothallium. The apical cell of the leaf is 

 first formed, then that of the root, and later that of the stem. No foot 

 is produced. The later stages are like those of an ordinary embryo of 

 fertilization. (6) At no time have nuclear migrations and fusions been 

 observed to occur in the prothallium when the embryo begins its 

 development. (7) At the stage when the sporangium contains eight 

 sporogenous cells an incomplete nuclear and cell division occurs in each 

 of these eight cells. As a result of the incomplete divisions, each 

 nucleus contains the diploid number of chromosomes — between 120 and 

 130. The eight sporogenous cells, now diploid, function as spore mother- 

 cells. The resulting spores are haploid, with 60-G5 chromosomes, a 

 number which is retained in the cells of the gametophyte and of the 

 apogamously developed sporophyte. (8) Thirty-two spores are ordinarily 

 formed in a sporangium of Nephrodium hirtipes. The smaller number 

 of spores, sometimes occurring, is due to abnormalities of the nucleus of 

 the spore mother- cell. (9) Sometimes more than thirty-two spores are 

 produced owing to the formation of more than four spores from a single 



