FEETILIZATlOJf AXD FRtJIT-FORMATION IN CORTPTOGAMS. 67 



all of which are classed ix^ther under the name of Vascular Ciyptogams, on account 

 of the presence of vascular bundles in their stem-structures and phyllodades. 

 The first generation of these Vascular Cryptogams, whereon are developed the 

 aatheridia and fruit-rudim^ats, also resembles in an unmistakable manner the first 

 generatioa in certaia liverworts. 



In Ferns, which constitute the most extensive section of the Vascular Crypto- 

 gams, and may be taken as their type, the first generation makes its appearance in 

 the form of a flat, green, foliaceous structure, usually reniform or heart-shaped, 

 lying in dose contact with the nutrient soil (see fig. 189 ^®). Inasmuch as the tissue 

 of this first generation nowhere contains vascular bundles, it must be looked upon as 

 a thallus, and has received the name of proUuMium. The Fem-prothallium bears the 

 fruit-rudiments as well as the antheridia upon its under surface, which is in contact 

 with the nutrient soil, and which adheres to it by means of a number of delicate 

 hair-Uke suction-ceUs. Some Ferns develop the froit-rudiments and antheiidia on 

 separate prothaUia: others produce them both on the same prothallium. In the 

 latter case the fmit-rudiments are situated near the sinus of the prothallium, and 

 tiie antheridia on the part remote from the sinus. Each froit-mdiment may be 

 compared to a flask ia shape, and arises from a superficial cell of the prothaUium 

 which is only slightly arched outwards. This cell is divided by the insertion of 

 two partitian-walls into three cells, each of which is again s^mented in definite 

 directions. From the uppermost cell is produced a tissue which forms the neck of 

 the flask-shaped fmit-mdiment; the middle cell gives rise to three cells^ of which 

 the two npper, the canal-cells, occupy the neck, whilst the undermost one becomes 

 the relatively large and sabsequently rounded ooplast. The daughter-cells de- 

 veloped from the lowest primary cell take the form of an investing wall round the 

 ooplast, or, to return to the analogy of a flask, constitute the wall of the ventraUy 

 enlarged poitian of the flask. The jootoplasm of the ooplast is the ooplasm, and 

 is now to be seen surrounded by a pluricellular tissue, which, as in the case of 

 Chaiaceae and Musdnese, may be called an amphigonimn. Only the neck of the 

 amphigonium projects above the other adjacent tissues of the prot»h»Tlium ; the 

 enlarged ventral portion is, as it were, sunk in the substance of the protibLaUinm. 



The antheridia axe also developed from cells npon the surfeee of the pro- 

 th«llimn These cells project in the form of papillse above the suxronndiDg tissae 

 and undeigo division by the introduction of partition-walls. The outermost 

 daa^ter-ceQ becomes enlarged and a^umes a globular shape, and from tiie proto- 

 plasm in its interior are formed spiral sp^cmatosnids. Another mode of or^iD 

 condsts in the formation of a papiDiform or hemisph^ed profaaiberance of tissue 

 which shows nnmistakabfy a di&rentiation into eraifacal cells destitute of diloro- 

 fhjB. and envelcq^ng ceDs containing chlorophylL The farmer divide up and a 

 fiUing-in tissue is formed, the small constitnQit eeBs of which contain spermato- 

 plasm. After the development of a spermatozoid in eadi of these small ceDs, tiie 

 whole of the fiBing-in tissue falls to pieces, tiiat is to say, the individual cells 

 separate from one anotiier and remain for a shcnt time disconnected but still in 



