5 



I 



During recent years Saccardo has included these plants in his 

 Sylloffe, listing first Patouillard's species Seuratia coffeicola 

 = A, Millardetiy Eac.) in the supplement which appeared in 1905 

 (vol. xvii. p. 558). Subsequently he adopted the name Atichia^ 

 and in a later supplement (vol. xxii. p. 769, Aug. 1913) he 

 records under that name all species which had appeared up to 1910, 



STRTJCTUItE. 



The structure of the Atichia thallus agrees in a general way 

 with that described for the Dominica plant. The thallus itself is 

 either an irregular wart-like or coralloid mass, or a flattened more 

 or less stellately branched body attached below by a small central 

 point. It is composed of a system of torulose almost articu- 

 lated filaments held together in mucilage. The filaments branch 

 irregularly and probably anastomose; towards the periphery the 

 branching is dichotomous and the cells smaller and more closely 

 packed, so that a denser cortical layer results- These terminal 

 cells are not, however, laterally united, but remain free as in 

 such an alga as Nemastoma. The mucilage is derived from the 

 outer layers of the cell-wall, and the amount present varies con- 

 siderably (in different specimens, being most abundant in old 

 plants. The thallus is colourless within, but externally it is 

 black, owing largely to the peripheral cells being dark in colour. 



Three kinds of reproductive organs are known, ascospores, 

 conidia-like cells which adhere in clusters, and pycnidia. With 

 regard to the asci, no definite apothecia or perithecia are produced, 

 but any part of the upper surface of the thallus may become fertile 

 and develop asci between the moniliform filaments in the cortical 

 layer. In some species the fertile portion is swollen in the form 

 of cushion-like pads, which in extreme cases may almost amount 

 to discoid branches. The asci are oval and contain two-celled 

 hyaline or subhyaline spores.* The conidial type of reproduction 

 is even more unusual than the ascigerous. The spores do not 

 occur singly but in clusters, each of which remains intact on libera- 



tion, and are produced in great quantities in cavities in the 



thallus. Mangin and Patouillard, wno have carefully worked out 

 the development, term these cell-clusters "propagula,^' and com- 

 pare them with the soredia of lichens. There is little doubt that 

 they represent a very abnormal form of conidial development. 

 The propagula themselves are produced in dense masses in the 

 circular or elongated cavities, and are well illustrated in Mangin 

 and Patouillard's paper('12,Fig. 1). The development of the cells 

 composing the propagulum is remarkable, and consists of sue- 

 cessive budding in certain definite directions. The whole thus 

 assumes a characteristic form, which is sufficiently well marked in 

 the different species to afford good specific characters. The genus 

 Phycopsisy formed for the reception of Seuratia Vanillae^ differs 



*RaciboTski states ('00, p. 41) that the spores of his species are brown, 

 and later ('09, p. 370) that tliey are (merely) brown-walled ('* hellbraun- 

 wandig "). An examination of the type specimens kindly forwarded to 

 Kew by Prof. Raciborski shows that when still in the ascus the spores are 

 practically hyaline, though it is possible that if examined on the spot after 

 natural dehiscence they may be brown-walled. 



