84 SUMMARY OF CURRENT RESEARCHES REL.VTIXG TO 



out the participation of the nuclei, by a rearrangement of alveolar 

 planes. The simultaneous mitosis in gametogenesis is a phylogenetic 

 reminiscence, and was of value in ancestral forms in increasing the 

 number of gametes. The supernumerary nuclei are phylogenetically 

 gametes. The receptive papilla is the result of a softening of the 

 oogonial wall by the oogonial contents ; while the receptive spot is a. 

 differentiated region of the oosphere. 



The four species, A. Portulacse, Bliti, Tragopogonis, and Candida, 

 constitute a series in which the ccenocentrum increases in complexity, 

 the receptive papilla decreases, and the number of functional nuclei 

 decreases. The ccenocentrum was an important factor in evolution from 

 the multinucleate to the uninucleate condition of the oosphere. The 

 division of the fusion-nucleus before passing to the winter condition is- 

 a consequence of the uninucleate condition, and constitutes the initial 

 step in germination. 



The paper concludes with a statement of the author's views as to the 

 phylogenetic relationship of Albugo to other genera belonging to the 

 Phycomycetes, — Peronospora, Saprolegnia, Pythium, &c. 



New Chytridineae.* — In the commencement of an account of the 

 narcological flora of Roumania, J. C. Constantincanu describes several 

 new species of Chytridineae, parasitic on fresh-water algae, and com- 

 pletes the hitherto imperfectly known cycle of development of other 

 species. 



Penicillate Tubes of Phyllactinia.f — P. Vuillemiu now confirms 

 Neger's statement that the penicillate tubes on the perithece of Phyllac- 

 tinia spring from the outer wall of the upper portion of the perithece. 

 When the perithece falls off, it lies in an inverted position ; and these 

 gelatinous tubes then fix it to the substratum. The author compares 

 these tubes to the periphyses which clothe the canal of the ostiole of 

 the perithece of many Pyrenomycetes. 



Variability of Lichens under different external conditions.} — 

 G. Bitter treats of this subject copiously, his observations, chiefly made 

 on species of Parmelia, being arranged under the following heads: — 

 The behaviour of certain lichens according to the angle which the sub- 

 stratum makes with the horizontal ; the conditions of the transition from 

 vegetative growth to soral formation ; the relationship of the production 

 of apotheces and soredes, dependent on external conditions ; the in- 

 fluence of external conditions on the growth and form of the sorals ; 

 the conditions for the formation of isidia-like branchings in Parmelio) 

 physode8 and P. tubulosa ; the influence of the intensity of illumination 

 on the colour and structure of the thallus ; the disposition (Felderungy 

 of the assimilating surfaces of various lichens by portions destitute of 

 gonids, and the influence on them of the conditions of the habitat ; 

 the influence of the thallus on the structure of later branchings within 

 its closed central portion ; variations in individuals of the same species 

 under similar external conditions. 



* Rev. Gen. de Bot. (Bonnier), xiii. (1901) pp. 369-S9 (15 figs.), 

 t Rev. Mycol., xxii. (1900) pp. 124-5. See Bot. Centralbl., lxxxviii. (1901> 

 p. 161. Cf. this Journal, 1900, p. 494. 



% Pringsheim's Jahrb. f. wisa. Bot., xxxiv. pp. 421-92 (7 pis. and 9 figs.). 



