127 



crushed at the same time. With care, however, they can 

 be got at, when they will be seen, as at D, covered with 

 warts or coarse reticulations, and beautifully regular and 

 perfect in outline : when young they are of a pure warm 

 sienna colour, and when perfectly mature, brown-black and 

 shining. They are sphasrical or slightly egg-shaped, and 

 measure on an average about one-thousandth of an inch in 

 diameter. I consider it worthy of special note that these 

 resting-spores are almost exactly the same in size, conforma- 

 tion and colour with Peronospora arenarige, Berk., an allied 

 species found parasitic on Arenaria trinervis. In looking 

 for these bodies care must be taken not to confound them 

 with corroded cells, granules of starch injured by the 

 disease, or foreign bodies. 



At E is shown a semi-mature resting.spore with pollino- 

 dium attached, accidentally half washed out of its coating of 

 cellulose by maceration in water. 



I may say as an addendum thut to me there is a 

 marked analogy in size aDd habit on the one hand between 

 the oogonia and the swarm-spores, and 011 the other hand 

 between the simple- spores and the antheridia. I consider 

 that the oogonia and antheridia are merely the intercellular 

 condition of the swarm -spores and conidia, which latter are 

 the aerial state of the former. 



The facts which point in the direction just indicated 

 are these : Sometimes there is no differentiation in the 

 contents of the swarm-spores, but the plasma is discharged 

 in one mass and not in the zoospore condition, the swarm- 

 spore then resembles the oogonium. At other times the 

 oogonium shows a distinct differentiation in its contents, and 

 matures from one to three resting-spores, which to me 

 shows an approach to the condition of the swarm-spore. 

 Wortliington G. Smithj Milway Grove. 



