1 66 



DIVISION II. COURSE OF DEVELOPMENT OF FVXGI. 



A second series of forms are intracellular parasites in the living and otherwise sound 

 foliage of some of the marsh plants infested by the first mentioned group. They form 

 brown spots or pustules on the leaves, and spread from cell to cell, and often produce a 

 large number of sporangia in each cell without coming out to the surface of the plant. 

 To this group belongs the form which has been described as Protomyces Menyanthis, 

 and another which may be named provisionally Cladochytrium Iridis. All the 

 sporangia in these two species are converted, as the mycelium disappears, into thick- 

 walled often brown ellipsoid resting-spores (Fig. 77), which, as far as is known, germinate 

 only after hibernation and then form swarm-spores. This was observed by Goebel, as he 

 informed me by word of mouth, in Cladochytrium Menyanthis, and by myself in C. Iridis. 

 The germination of the swarm-spores has not yet been observed. 



The occurrence of members of both these groups in the tissue of the same plant, as 

 for example in Iris Pseudacorus, might lead to the supposition that the forms of the first 

 group belong to the same species as those of the second which form resting-cells ; but 

 there is no fact to show this, and it is opposed to the observation that a large number 

 of swarm-spores of Cladochytrium Iridis will not germinate even on dead tissue of Iris 

 Pseudacorus. They seem to require living cells for their further development, but 

 I could not see that they made their way into them. 



No act of conjugation and no sexual organs 

 have been observed in these plants. In the 

 formation of intercalary sporangia and resting- 

 cells it is often observed, that an intercalary 

 swelling of a branch of the mycelium first 

 appears and is then divided by a transverse wall 

 into two halves ; one of these halves swells into 

 a sporangium, while the other does not enlarge 

 and loses its protoplasm. But it cannot be 

 seen that the protoplasm has passed over, as 

 might be supposed, into the half which is in- 

 creasing in size, it seems on the contrary to 

 travel into the growing mycelium ; and on the 

 other hand the whole of Ihe part that swells at 

 first often becomes a sporangium or resting-cell 

 without previous transverse division. The con- 

 jugation of the swarm-spores, which might also 

 be expected from analogy, has not been ob- 

 served. 



The forms of Physoderma, Ph. maculare, Wallr. inhabiting Alisma graminifolium, 

 Ph. Heleocharidis, Fuckel, Schroter's (i 882), Ph. Butomi and Ph. vagans, the latter of 

 which is found in different Phanerogams (Potentilla anserina, Ranunculus flammula, 

 &c.), are very like Cladochytrium Menyanthis and C. Iridis as regards the intracellular 

 development and the structure of their resting-spores in the inner layers of the 

 parenchyma of the leaves of their host. But these species according to Schroter have 

 no mycelium; the single resting-spore is formed in the same way as in Synchytrium. 

 We are not told how their primordia find their way into the interior of the cells. 



SECTION XLIX. 3. Olpidieae. We are indebted to A. Fischer for a com- 

 plete account of the development of Olpidiopsis Saprolegniae and O. fusiformis, 

 Cornu. The former plant causes a pouch-like swelling in the tubes of the 

 Saprolegnieae which it inhabits, and in its full-grown state is an ellipsoid or round 

 cell which forms neither rhizoids nor mycelium, but ultimately becomes a sporangium 

 and discharges its zoospores through one or more cylindrical necks which pierce 



FlG. 77. Cladochytrium Iridis. a a resting-spore 

 with a brown membrane seen from the broad side, b the 

 same rotated through 90 ; in its centre a large sphere 

 of fatty matter, c i successive stages of germination of 

 a resting-spore ; the inner cell developes into a tubular 

 swarm-s|>ore-receptacle, when the brown outer membrane 

 has opened by a lid. d completion of the formation of 

 the spores, c exit of the spores, /"a single swarm-spore. 

 ae magn. 375, f 500 times. 



