IN THE VEGETABLE KINGDOM. 35 



the unwalled contents of the latter, which are then converted 

 into a spore, the soft mucous investment being transformed 

 into a consistent cell-wall. 



The latest observations on Vaucheria we owe to Prings- 

 heim,* who has also directed much attention to the corres- 

 ponding processes in Aclilya (Saprolegnia Kutz.J, a genus 

 really closely allied, though of very different external ap- 

 pearance, the filaments being colourless and much more 

 minute, and growing like a tuft of mouldiness on dead flies 

 and other animal matter macerating in water. The sporan- 

 gium has here the same general relations as in Vaucheria, 

 but their walls are perforated by a great number of pores, 

 and they contain eventually numerous spores. Although 

 no antherozoids have yet been detected, the antheridia 

 appear to be represented by slender vermiform branchlets 

 which arise between the sporangia, and sometimes twine 

 round them in irregular coils. These, according to Pring- 

 sheim, throw out lateral papillae, which protrude into the 

 pores of the sporangia.-f- 



Both these genera propagate usually by gemmae de- 

 veloped in -the dilated extremities of the branches, which 

 are converted into cells by the formation of transverse septa 

 in the filaments. In Vaucheria the whole contents, when 

 mature, are thrown out through a perforation in the apex 

 of the cell, as one large ciliated spore; mAchfya they break 

 up into a swarm of motile corpuscules like the zoospores of 

 other Algae. It is not ascertained whether the co-existence 

 of these two kinds of reproductive bodies is connected with 

 any form of alternation of generation ; no phenomena of 

 the kind have yet been observed in this group. 



* Quart. Journ. Micr. Sc., IV., 63, 130. 



f Braun, Nsegeli, and Karsten supposed that a real conjugation of 

 cells took place in Siphonese ; but the view founded on the late observa- 

 tions of Pringsheim is now generally received. Achlya, however, is still 

 considered by some as merely the early phase of a true mould or fungus. 



