TWENTT-SEYENTH ANNUAL MEETING. 161 



and Orthotrichum. Sometimes the apex is straight, and again it is inclined; 

 sometimes it is split up one side, or cucullate; or it may be cone-shaped, with a 

 smooth or irregularly-lobed base, it then being termed mitriform. (See plates.) 

 The capsule or theca varies much in size, shape, surface, and color; but the gen- 

 eral iorm is cylindrical or globose. These forms are modified in many ways, into 

 intermediate shapes, as very long cylindrical, pyriform, elliptical, oval, angled, 

 straight or curved, erect or corneous, or pendulous. Again the capsule may be 

 constricted or widened at the mouth or throat ; having a very small or large lid ; 

 and sometimes the base is enlarged (called the apophyses); or if only «ne side is 

 swollen it is termed strumose. 



The walls of the capsule are always several layers thick, with a distinct epi- 

 dermis, and frequently with stomata. Only a fjart of the central tissue of the 

 sporophore is used in the growth of the spheres; except in Archidium, where it 

 is all finally displaced by the matured spores. 



The columella is the central tissue of the capsule, and the mother cells of the 

 spores are formed around it; but the manner of this growth is characteristic in 

 each group of mosses. (See "GoeVjle's Special Morphology," pp. 177-178, and 

 "Sach's Botany," pp. "374-375.) 



The interior of the capsule may develop in four different ways; and, upon 

 this difference, mosses are divided into four divisions or orders. 



The central cells of the theea are called the endothecium, and the pe- 

 ripheral cells, the perithecium The endothecium develops an outside layer of 

 cells by division, called the archesporium, which is the spore-forming tissue. 

 This archesporium divides into a mass of spore mother-cells, each of which 

 divides into four spores. 



The perithecium grows and forms by cell division, several layers of cells; 

 two of these layers usually being next the archesporium, with an interior 

 cellular space between the outer layers several cells in thickness. This outer 

 layer is connected with the inner layer covering the archesporium (called 

 the outer spore sac). (See Sach's Botany, p. 378.) 



The four types or natural divisions of mosses,' based upon the development 

 of the spores in the capsules, are as follow: The first and simplest is Sphagna- 

 ceae, in which the endothecium forms the columella only, which does not 

 pass through the archesporium, but is covered by it above. 



The second type is Archidiaceae, in which the fertile and sterile cells are 

 mixed together in the endothecium, and the spore sac is separated from the 

 wall of the capsule by a bell-shaped intercellular space, and there is no col- 

 iimella. 



The third type is Andreaeaceae, in which the endothecium is differentiated 

 into archesporium and columella, but the columella does not pass through 

 the archesporium. The inner layer of the amphithecium becomes the spore 

 sac, which is not separated from the rest of the parietal tissue by an intercel- 

 lular space. 



The fourth type, Bryaceae, is similar to Andreaeaceae, except that the col- 

 umella passes through the spore sac, which is separated from the walls of the 

 capsule by an intercellular space in the shape of a hollow cylinder. 



The operculum covers the top of the capsule, like the lid of a sugar bowl, 

 assuming many shapes and sizes, and varying from the usual conical to long- 

 beaked (rostellate), or plano-convex. The apex may be mamillate, apiculate, 

 straight, or bent, while the surface may be either rough or smooth and the 

 color the same as or different from the capsule, and in many cases forming 

 a specific distinction between the species. (See plates.) 

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