MONOBLEPH ARID ALES 699 



The thallus and sporangia of Monoblepharella taylori resemble in 

 superficial aspect those of Monoblepharis regignens and M. ovigera. The 

 mycelium, which forms a lustrous pearly-gray halo around the sub- 

 stratum, is composed of delicate moderately branched hyphae 2-3 jjl in 

 diameter. Near the base, where the plant is anchored by a system of 

 holdfasts to the substratum, the hyphal axes may attain a diameter of 

 5 [x. Catenulate series of swellings are formed on the hyphae of some, 

 but not of all, isolates. The hyphal contents are characteristically arrang- 

 ed in a rich network or reticulum, within which somewhat coarse 

 refractive granules of irregular size may be seen moving. A preliminary 

 cytological examination of the hyphae shows the minute nuclei to be 

 disposed at more or less uniform intervals. 



REPRODUCTION 



Nonsexual Reproduction 



In most species of Monoblepharis, at about 8-1 1°C, only nonsexual 

 reproductive organs are formed. These are usually terminal, slightly 

 swollen, cylindrical portions of the hyphae, with homogeneous contents. 

 Each sporangium is finally separated by a cross wall from its adjacent 

 hypha. According to Laibach (1927), the nuclei are at first more or less 

 regularly placed in the hyphae (Fig. 48 F, p. 700). As the rudiment of 

 the sporangium begins to develop there is an increase in the number of 

 nuclei in that body (Fig. 48 G-H). No mitotic figures were observed in 

 the process of sporangial formation by either Lagerheim (1900) or 

 Laibach. It remains a question, therefore, whether this increase is due 

 to a migration into the sporangium or to the division of a few nuclei. 

 As the cross wall is laid down the nuclei become more or less equidistant 

 from one another (Fig. 48 I). A central vacuole appears during differen- 

 tiation of the zoospores (Fig. 48 J). Coincident with spore cleavage there 

 is a marked increase in the size of the individual nucleus, which now 

 exhibits around its periphery masses of dark-staining material. Laibach 

 suggests that this material may be connected with flagella formation. 



The cleavage planes of the spores appear in most instances to be at 

 right angles to the long axis of the sporangium, although many may be 

 obliquely placed (Fig. 48 K, p. 700). The spore initials are at first angular 



