268 SUMMARY OF CURRENT RESEARCHES RELATING TO 



length, a transverse wall makes its appearance, which is then followed 

 by others. These transverse walls are of great thickness, often ten 

 times as thick as the lateral walls ; and their surface is irregularly wavy, 

 giving them great refringency. For a time there is not unfrequently a 

 circular orifice in the middlo of these " heams." In addition to these 

 there are " irregular " septa, consisting simply of excrescences of 

 cellulose from the lateral and longitudinal walls. While the outer walls 

 grow by intussusception, the transverse walls grow by the apposition of 

 layers of cellulose. The orifices in the walls of both antheridia and 

 oogones, through which the spermatozoids reach the oosphere, appear to 

 be formed during the development of these organs. 



On the point of the presence of a nucleus in the cells of Spliseroplea, 

 Eauwenhoff corrects his former statement, and now asserts that, by the 

 use of the proper reagents, a larger number of very small nuclei can be 

 detected in the mature cell. The very young plant contains a single 

 nucleus with a distinct nucleolus ; at a later period two may be seen, 

 and then the number rapidly increases, probably by division. 



Ulothrix crenulata.* — From an examination of this alga, found 

 growing on the trunks of trees, M. E. de Wildeman confirms the obser- 

 vations of Gay | on the formation of cysts in the Chlorosporeae. A 

 gradual transformation of the cells of this species takes place into a 

 form indistinguishable from Pleurococcus, exceedingly similar to the 

 corresponding changes in U. radicans. The form known as Schizogonium 

 may probably be regarded as another phase in the life -history of the 

 same organism. 



Alga epiphytic on a Tortoise. $ — Mr. M. C. Potter describes an alga, 

 previously detected by Peter,§ and named by him Dermatophyton radicans, 

 growing principally on the dor.-al surface of the carapace of the water- 

 tortoise, Clemmys caspica, where it forms irregular roundish dark-green 

 patches often about 1/4 of an inch in diameter. No sexual reproduction 

 was observed, the alga being propagated by means of zoospores formed 

 from the outermost layers of cells, without conjugation. The author 

 considers it probable that it must be ranked under the Ulvacese. 



Formation of Auxospores in Diatoms. ||— Herr F. Schiitt states that 

 in the genera ffliizosolenia, Orthosira, Melosira, and other forms nearly re- 

 lated, he has been able to detect no indication of any process of sexual 

 reproduction. In Cocconema, Frustulia, and most Naviculacese, two 

 naked cells, separated by gelatinous layers, lie side by side, but do not 

 unite, each of them becoming an auxospore. In Himantidium (Eunotia) 

 the two naked juxtaposed cells unite into a single auxospore ; while in 

 Epithemia the two cells divide transversely, the two halves of each cell, 

 which lie opposite to one another, uniting into an auxospore ; each 

 auxospore therefore including one-half the contents of the two cells. 



Fungi. 



New Forms of Mycorhiza.ir— Herr B. Frank states that he has 

 observed the following distinct colours in mycorhiza-filaments on the 



* CR. Soc. R. Bot. Belg., 1887, pp. 119-23. f See this Journal, 1887, p. 277. 



X Journ. Linn. Soc. Lond.— Bot., xsiv. (1887) pp. 251-4 (1 pi.). 

 § See this Journal, 18S7, p. 123. 



|| Biol. Centralbl., vi. (1887). Cf. this Journal, 1886, p. 832. 



i Ber. Deutsch. Bot. Gesell., v. (1887) pp. 395-409 (1 pi.). Cf. this Jourual, 1886, 

 p. 113. 



