220 NOTICES OF BOOKS AND MEMOIRS. 



capsule, and especially in the innermost of them, increase in size 

 continues ; the number of the constituent cells is doubled by 

 means of radial walls, and the air-chamber enlarges. At the same 

 time, the cells of the outer spore-sac increase to a moderate extent, 

 and those of the spore-layer vigorously, by radial walls, the latter 

 also enlarging in the direction of the radius, and thus pressing 

 together the former. When the spore-layer consists of eight cells 

 in transverse section, the cells of the columella commence dividing, 

 the succession of segmentation corresponding with that seen in 

 the original quadrant-cells. The outer layer resulting from this 

 process constitutes the inner spore- sac ; while it is going forward 

 the rupture between the third and fourth layers advances inwards 

 above and below ; by this means are formed the two short columns 

 which retain the tissues inside the air-chamber in connection with 

 the top of the capsule and with the apophysis : each of them 

 consists of four rows of cells in longitudinal section. Meanwhile 

 the cells of the layer bounding the air-chamber externally become 

 vaulted into that chamber, and rounded at the opposite side, so 

 that intercellular spaces make their appearance between this and 

 the second layer. Some of the cells of the third layer then divide 

 radially, and whilst the two daughter- cells are vaulting inwards so 

 as finally to encroach on their neighbours, the se^Dtum between 

 them divides in the middle ; thus is formed a stomate affording 

 commmiication between the air-chamber and the intercellular space 

 just mentioned. 



The development of the sporogonium of Ceratodon jnirpureum is 

 essentially similar (exception made for minor differences of struc- 

 ture) to that of Phascurn. In this species, each of the last-formed 

 (peripheral) cells of the young capsule undergoes periclinal division, 

 so that the laj^er immediately bounding the central square is com- 

 posed of eight cells in transverse section, the following one of 

 sixteen, the next of thirtj^-two, and the two outermost of sixty- 

 four cells. The formation of the air-chamber (between the fourth 

 and fifth layer countmg from outside) of the spore-layer, inner 

 spore-sac, columella, and stomata is the same as in Fhasciim. 

 The author has minutely worked out and figured the development 

 of the peristome, the result being that the entire peristome belongs 

 to the amphithecial region, the outer cells of this structm-e being 

 continuations of the fourth or air-chamber-bounding layer, and its 

 inner cells of the outer si)ore-sac. 



In the growing capsule of Funaria }uj(jrometrica the formation 

 of the central square does not take place by means of two walls 

 (an anticlinal and a periclinal) at right angles to each other, but 

 by the laying down of a single perichnal wall. By a process 

 similar to that which we have seen in Ceratodon, the amphithecium 

 at length consists of nine layers. In the zone of the annulus, 

 however, and beyond it is composed of onty six layers. The 

 peristome in this species is developed from the fourth, fifth, and 

 sixth cell-layers (counting from the outside) ; it is, therefore, 

 entirely amphithecial. Each cell of the central square divides by 

 a periclinal and an anticlinal wall at right-angles to each other 



