204 



MONOGRAPH OF THE LABOULBENIACE.E. 



The transfer of the spores from one host to another is probably accomplished, as 

 a rule, by the direct contact of two insects ; as, for example, during coitus, perhaps 

 never otherwise in the aquatic species, as might be inferred from the remarkable con- 

 stancy with which some of these forms occur in definite positions on the elytra or else- 

 where ; but may doubtless be otherwise effected, at least in cases where more or less 

 gregarious hosts inhabit or hide during the day in moderately moist situations. Under 

 these conditions it is not improbable that spores discharged upon materials with which 

 such insects have come in contact may subsequently adhere to other individuals on 

 which they may develop. Although a gelatinous envelope is always a protection of 

 extraordinary efficacy, it does not seem probable that the spores can retain their 

 power of germination for any considerable time, at least in a dry condition. 



Having reached a proper host, and having adhered to it by virtue of its generally 

 viscous character, the spore begins to germinate at once. 



Germination. The first indication of germination in the spore usually consists in 

 the modification of its lower extremity into a blackened organ of attachment, the foot ; 

 the blackening resulting from a change which takes place in the gelatinous envelope 

 in this region by which it becomes converted into a black, opaque, hardened, more or 

 less elastic medium of attachment to the host. This conversion of the lower portion 

 of the basal spore segment into an indurated organ by which the growing plant ad- 

 heres firmly to the substratum on which it grows, is apparently unconnected with any 

 effect resulting from contact with the chitin of the insect ; since, in exceptional in- 

 stances, where the usual discharge of spores has been prevented from any cause, the 

 latter, while still within the perithecium, may begin to germinate and even attain an 

 advanced development (Plate V, figs. 1 and 19). In such cases the first step in the 

 process consists, as in normal germination, in the formation of a blackened foot of the 

 usual type. A foot of this nature is not, however, invariably present. If the figures 

 of Peyritsch are to be relied upon, there is no such blackening in the case of Helmin- 

 thophana (Plate VIII, fig. 10), which is represented as penetrating the integument of 

 the insect on which it grows by the intrusion of a papillate haustorium, there 

 being no blackening whatever of the basal cell. The typical foot is also conspicu- 

 ously absent in certain other genera. In Moschomyces also, to which reference has 

 been made above, this organ is not differentiated ; and the plant penetrates the soft 

 integument by means of a cellular haustorium which, expanding within the body cav- 

 ity of the host, holds the parasite firmly attached. The most striking exception, 

 however, is presented by the genus Rhizomyces, in which the penetrating haustorium 

 reaches a development quite beyond that of any other form. In this case (Plate 



