796 Betts . — A Bee-hive Fungus , Pericystis alvei , Gen. et Sp. Nov . 
larger; 8-6 x 7-5 /x are average measurements. 1 The walls of these spores 
are thicker than those of the ordinary hyphal cell ; this, together with their 
frequently isolated position, is felt to justify the use of the term chlamydo- 
spore rather than that of oidium-cell, although they resemble the typical 
oidium-cell in their capacity for immediate germination. 
If a comb on which Pericystis alvei is present be examined in the early 
spring, 2 some cells will be found in which the fungus is no longer white, but 
grey. In May it is not unusual to find specimens of a dark slate-grey 
colour. This change is due to the formation of the cysts. These are sub- 
globose or irregularly oval objects 20 ju (occasionally less) to 40 x 30 /x 
(average about 30 /x in diameter), 3 and contain numerous spores. The cyst- 
wall is thin, smooth, and structureless, semi-transparent, and has a polished 
appearance when viewed by reflected direct sunlight. It is dark green in 
colour, appearing black by reflected light. Each cyst is borne on three to 
five short hyphal branches, also of a dark green colour. The general 
appearance of a culture with mature cysts is shown in PI. LXXVI, Fig. 10. 
The walls of the mature cyst and its supporting hyphae are not 
dissolved when placed in concentrated sulphuric acid on a slip, covered 
with a cover-glass, and heated till bubbles are expelled. 
The cyst-spores are hyaline, spherical, and thick-walled (PI. LXXV, 
Fig. 9) ; they are 37-47 /x in diameter, average 4-3 /x. The number present 
in a cyst is variable, depending on the dimensions of the cyst. So far they 
have not been observed to germinate. Possibly they require a resting period, 
or conditions different from those which are favourable to the germination 
of the chlamydospores. 
The cyst arises as a swelling or lateral projection on a hypha. This 
puts out one or two (rarely three) processes, which fuse with a neighbouring 
hypha, usually bending through a right angle to do so (PI. LXXV, Figs. 4, 5). 
The young cyst now increases in size, and its contents assume a vacuolated 
appearance (PI. LXXV, Fig. 6). The wall presently begins to acquire a 
brownish tint ; a culture at this stage is of a pale salmon or bone colour to 
the naked eye. The tint deepens, till finally the wall turns green ; it almost 
attains its mature depth of colour before the spores begin to be visible 
within the cyst (PI. LXXV, Fig. 7). 
The fusing hyphae become septate at an early stage. Inspection of 
stained material reveals that there are three septa ; one at the junction with 
the cyst, and two others close together further along the hypha (PI. LXXV, 
Fig. 7). The contents of the young cyst are highly granular, and the septa 
are in consequence frequently invisible in unstained material. 
1 Measurements taken from honey-gelatine culture material. 
2 Possibly in mid-winter also. Grey specimens were plentiful on some material in January ; 
but these combs were from hives where the bees had died, so that the conditions were not normal. 
3 Measurements taken from honey-gelatine culture material. 
