312 



MANUAL OF POISONOUS PLANTS 



is brought about. After fertilization, the egg cell divides and gives rise to an 

 embryo. The mosses diflfer from the ferns and their allies in a less differentiation 

 of tissues and a slight development of shoot and root S3'stem. The vascular 

 system and leafy shoots and roots are marked in the ferns. 



PTERIDOPHYTA 



Spores alike or unlike microspores and megaspores developing into flat or 

 irregular prothallia ; these bear the reproductive organs, (antheridia and arche- 

 gonia) ; flowers and seeds absent; usually a well developed vascular system.. 



This sub-division includes the class Filicales or ferns proper. The class 

 Equisctales or horsetails; the Lycopodiales represented by the common club 

 moss, {Lyco podium). 



Fig. 116b. Fern. A. Section through frond of As- 

 tidium Filix mas, a leaf-like body with parenchyma cells, 

 an epidermis and vascular bundles x 100. B-J. Develop- 

 ment of the sporangia of Aspidium trifoliatum x 350. K. 

 Young sporangium of Nephrolejns cxotlcta in the act of 

 differentiating the annulus x 350. L. Immature sporangium 

 of Blechnum occidentale, seen from the back. M. Sporangi- 

 um with spores. N. Sporangium dehiscence at st, a jointed 

 ring X 120. O. Group of sporr mother-cells x 350. P-R. 

 Single spore mother-cells in dilTercnt stages of partition 

 X 425. S,T. Bilateral tetrads of Aspidiuvi Filix tnas. U. 

 Mature spores of Aspidium Filix mas x 500. /'. Tetrads. 

 After Luerssen. 



