WITH NOTES ON OTHER SPECIES. 69 



The internal hyphse, whose office is the absorption of nourishment from the sub- 

 stratum, may properly be termed rMzoids, whether fi-om a morphological or a physio- 

 logical point of view. DeBary states ('81, p. 95) that the external hyphse may send 

 down rhizoidal branches which penetrate the substratum. Well-developed threads, 

 when cut off from their basal portions and brought in contact with fresh nourishment, 

 will attach themselves to it by new rhizoids and continue their growth. 



In addition to the protoplasmic contents and the food material diffused through 

 it, the hyphse of the Saprolegniacem contain more or less generally certain bodies as 

 yet unrecognized in other plants. They have been called by Pringsheim ('83 6), 

 cellulin granules (Fig. 6, c). They occur in the filaments or in reproductive organs 

 formed from them, as discoid or lobed bodies, those of the latter form arising by 

 fusion of several disks. When young, they are homogeneous and rather strongly 

 refractive; and when old they often become distinctly stratified. They are, perhaps, 

 most abundant and conspicuous in Leptomitus lacteus, where they were early 

 described by Pringsheim ('60) as nuclei. In this species they often become lodged 

 in the constrictions of the hyphse and may completely close the passage. Prings- 

 heim has shown ('83 h), that the substance of these bodies is neither a proteid nor a 

 carbohydrate, although it is in some respects related to cellulose and starch. He 

 regarded them as waste products of metabolism rather than as reserve materials, 

 since he saw no evidence of their solution or transformation. But Rothert has shown 

 ('88) that they probably contribute to the formation of the separating wall of the 

 sporangium, since they seem to disappear during that process. It may also be 

 suggested that cut hyphse may owe their power of promptly repairing injury to the 

 presence of this material. Should this be shown to be the case, they may be regarded 

 as a soluble form of cellulose available for use in forming and repairing cellulose walls. 



]^ON-SEX[JAL KePRODUCTION. 



After they have become well grown, the external hyphse begin to produce the 

 organs of reproduction, which are of two sorts, sexual and non-sexual. We will con- 

 sider these as they are developed in the order of time, examining first those of non- 

 sexual or vegetative reproduction. Only a single organ of this sort is common to 

 the entire family ; namely, the zobsporangium. Within this organ are produced the 

 agents of the rapid propagation of the species concerned, the zoospores. The phe- 

 nomena of the development and individualization of the zoiispores within the 

 sj)orangium appear to be essentially the same in most of the genera, at least. But 

 the manner of their release from the sporangium and their subsequent history 



