138 TRANSACTIONS AND PROCEEDINGS OF THE [sess. lv. 



same changes as take place in all other sporangia. The 

 normal way of spore-formation as found in Vascular Crypto- 

 gams starts with the development of several or of only one 

 archesporial cell, by the division of which sporogenous 

 tissue is formed, consisting at one time of sporocytes. These 

 cells have shortly after their formation thin but definite cell- 

 walls ; as they grow older the walls commence to swell, and 

 may at this stage be stained deeply with heematoxylin. 

 Ultimately each sporocyte is set free, assumes a globular 

 shape, and gives rise to four spores by repeated bipartition. 

 The spores resemble four tetrahedra with arched outer walls, 

 and may l)ecome globular on maturation, or may not. Study- 

 ing now the development of angiospermous ovules, we find 

 in Myosurm minimus and lianunculus sceleratus five to six 

 subepidermal initial cells surrounding a central cell, all at 

 first similar in appearance, but soon the central cell outstrips 

 the others in growth and becouKiS the physiological arche- 

 sporial cell ; in Rosa livida and Fragaria vesca four subepi- 

 dermal archesporial cells are formed ; in Lamium maculatum. 

 two occur ; while in the great majority of cases only one 

 arcliesporial cell is found. 



This arcliesporial cell may either always cut off a tapetal 

 cell, as in Vol tigoiivAn di'varicatuvi, Rosa livida, Fragaria 

 vesca, Tritonia aurca, Anthericuni ramosu7)i ; or may only 

 occasionally do so, as in Hancrocallis fuha ; or never do so, as 

 in Myosurm, Orchis pollens, Monotropa, &c. After the forma- 

 tion of the tapetal cell, if the latter is formed at all, the 

 archesporium or embryo-sac-mother-cell divides in Rosa livida 

 into five or six cells, the uppermost of whicii, usually, developes 

 into an embryo-sac. In Scnccio vidgaris, according to Warming 

 and Vesque, the archesporial cell divides occasionally into 

 five cells, althougli its division into four cells is the rule ; 

 in Lamium, maculatum. Salvia 2'n'atensis, Tritonia aurea, 

 Sisyrinchiuvi iridifolium, Hnncrocallis fulva, &c., the arche- 

 sporium divides into four cells, the lowest of which becomes 

 the eml)ryo-sac ; in Myosurus minimus division into only 

 three cells is the rule, but in a great number of cases my 

 pr(;parations show tliat tiic outermost cell, the one just 

 beneath the dermatogcn, divides again by an anticlinal wall, 

 so that the archesporium forms four cells ; in Anthericuni 

 ramosum, Orchis pallens, Tradcscantia virginica, Gymnadenia. 



