and its relation to that in the Animal Kingdom. 357 



as far as the formation of the mother-cells of the spores. In the 

 megasporc-capsule only one of these eontinues its development 

 — to the formation of four special mother-cells, and spores, all 

 of which here attain their full development. Accoi'diiig to Hof- 

 meister, the spore-capsule is not produced from the leaf upon 

 which it afterwards appears implanted, as assumed by V. Mohl*, 

 but arises from the cells of the stem just above the leaf. 



Five months after sowing, Ilofmeister saw small globular cells 

 in the microspores, in which cells were developed sjjirally-coiled 

 spermatozoids, moving slowly after they had emerged from the 

 cells t. 



Not until six weeks later occvirs the so-called germination of 

 the mcgaspores, the development of a prothalliuni bearing arche- 

 gonia, so that fecundation could only be possible when later- 

 sown microspores were present at this epoch. While the mega- 

 spore is still contained in its capsule, it exhibits at its upper 

 part (under the point where it was originally in contact with 

 the three sister-spores, at which place meet three ridges with 

 longitudinal slits, corresponding to the commissural angles) a 

 double layer of cells, of which it is not yet decided whether they are 

 produced by free cell-formation in the manner of the endosperm- 

 cells in the embryo-sac of the Coniferse, or by cell-division. A 

 few repetitions of the process of longitudinal and transverse 

 cell-division convert this layer into the Hat prothalliiun. At 

 several points on this arise archegnnia formed bv the horizontal 

 division of a cell bulging outwards, enlargement of the lower, new 

 cell into the central cell, and the successive division of the upper 

 into two tiers, each composed of four cells, the upper tier of 

 which alone projects from the surface of the prothallium. The 

 archegonial canal and the germinal vesicle are formed as in the 

 Rhizocarpese. The free space in the cavity of the spore situated 

 below the prothallium becomes gradually filled up with cellular 

 tissue which grows from above downwards. 



The first step in the formation of the embryo is the horizontal 

 division of the germinal vesicle. Ordinarily this is repeated a 

 number of times, with simultaneous longitudinal extension of 

 the newly-formed cells ; in this way is formed a pro-embryonal 

 cord of cells [suspenso?-) which penetrates downwards into the 

 cellular tissue filling the megaspore, and here first gives birth to 

 the body of the embryo, by the division of its end-cell by alter- 

 nately-inclined septa. The secondary axis is not produced from 

 the apical cell of the embryonal mass, but from one at the side, 

 quickly assuming an ascending direction, breaking through the 



* II. Von Mohl, Vermischte Scliriften, p. 106. 



t [We have found the spermatozoitls developed, but not yet moving, 

 after a much shorter interval than this. — A. H.] 



