222 



THAXTER. MONOGRAPH OF THE LABOULBENIACEjE. 



be apparent between the male and female spores in dioecious genera. It may be here remarked that 

 the cytological phenomena in this connection, which lead up to the sexual differentiation and pairing 

 in the ascus of these male and female spores, is likely to prove of unusual interest. 



Moschomyces and Compsomyces remain the only genera in which the presence of octosporic asci 

 has been definitely determined. The writer has been unable to satisfy himself, however, that this is not 

 also the condition in Herpomyces. If this were actually the case, it would involve the curious phenom- 

 enon of absolute sex differentiation in the last mitosis, which would not necessarily occur in a four spored 

 ascus. 



In almost all the species the first step in germination consists, after the spore has become attached, 

 or even before, in the formation of the familiar hoof-like organ of attachment and absorption, the foot: 

 an indurated, firmly attached, blackened rim, surrounding a thin membrane which is in direct contact 

 with the surface of the host and through which materials are absorbed into its cavity, the latter being, as 

 a rule, in direct communication with that of the basal cell of the receptacle; although, in some instances 

 at least, it is evidently separated by a septum, Plate XLIX, fig. 1G. 



The nature of this foot may be somewhat variable. In Coreomyces, for example, it may be modi- 

 fied to form a spreading, almost rhizoidal structure, Plate LXXI, fig. 14, of characteristic appearance 

 somewhat similar to that of Zodiomyces. The most striking departure from the normal type, however, 

 is seen in a relatively small number of species, and was illustrated in the writer's earlier Monograph (Mos- 

 chomyces and Rhizomyces). In these instances the parasite obtains its nourishment directly from the 

 body-cavity of the host by means of a penetrating intrusion. Such intrusions are usually associated with 

 growth on a thin or soft integument. Thus Moschomyces, in which the penetrating organ expands to 

 form a cellular cushion, grows on the thin integument beneath the elytra, or at the bases of the legs of 

 its otherwise hard-shelled host. But the most striking instances of this nature are seen in forms which 

 live on soft bodied Diptera, and produce a more or less well developed filamentous rhizoidal apparatus. 

 In Dimeromyces rhizophorus the thin skin on the under surface of the abdomen of a small fly is perforated, 

 as is shown in Plate XXVIII, figs. 6-8, and a stout tapering filament extends some distance into the 

 semi-fluid contents of the abdomen, furcate in the female, and simple in the male individual. A beauti- 

 fully developed branching rhizoid is seen in Ceraiomyces Dahlii, Plate "XLIII, fig. 4, and a still more 

 copiously branched organ of this nature is present in the species of Arthrorhynchus, the copious and 

 intricate branching of which is merely suggested in Plate XLVIII, fig. 2. 



It is a remarkable fact that the presence or absence of such penetrating organs is not necessarily an 

 attribute of all the species of a given genus, or even of those which grow on the same, or similar hosts. 

 Thus Ceraiomyces Selena and Rhizomyces crispalus both possess a typical foot, although all the other 

 species of these genera are rhizophorous. Dimeromyces rhizophorus, moreover, is the only species in a 

 considerable genus, which has this character; although the closely allied D. coa retains grows under 

 exactly the same conditions in the same position on a similar soft bodied host. In the genus Stigmato- 

 vajecs, the species of which with few exceptions occur on soft bodied flies, not a single instance of this 

 nature is known, nor does Laboulbenia Harjeni, on the delicate integument of the soft bodied Termites, 

 develop any intrusion from the normal foot figured, from below, in Plate III, fig. 4, of the former Mono- 

 graph. An isolated instance in which the usual foot is combined with a penetrating organ, occurs in the 

 genus Herpomyces, all the species of which possess slender simple rhizoidal threads, which penetrate 



