FERTILIZATION AND FRUIT-FORMATION IN CRYPTOGAMS. 67 



all of which are classed together under the name of Vascular Cryptogams, on account 

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

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

 antheridia and fruit-rudiments, also resembles in an unmistakable manner the first 

 generation in certain 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 close 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 prothalliuvi. The Fern-prothallium bears the 

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

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

 hair-like suction-cells. Some Ferns develop the fruit-rudiments and antheridia on 

 separate prothallia; others pi-oduce them both on the same prothallium. In the 

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

 the antheridia on the part remote from the sinus. Each fruit-rudiment may be 

 compared to a flask in shape, and arises from a superficial cell of the prothallium 

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

 two partition-walls into three cells, each of which is again segmented in definite 

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

 the flask-shaped fruit-rudiment; the middle cell gives rise to three cells, of which 

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

 the relatively large and subsequently 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 ^•entrally 

 enlarged portion of the flask. The protoplasm of the ooplast is the ooplasm, and 

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

 Characeffi and Muscine^, may be called an amphigonium. Only the neck of the 

 amphigonium projects above the other adjacent tissues of the prothallium; the 

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



The antheridia are also developed from cells upon the surface of the pro- 

 thallium. These cells project in the form of papillfe above the surrounding tissue 

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

 daughter-cell becomes enlarged and assumes a globular shape, and from the proto- 

 plasm in its interior are formed spiral spermatozoids. Another mode of origin 

 consists in the formation of a papilliform or hemispherical protuberance of tissue 

 which shows unmistakably a difterentiation into central cells destitute of chloro- 

 phyll and enveloping cells containing chlorophyll. The former divide up and a 

 filling-in tissue is formed, the small constituent cells of which contain spermato- 

 plasm. After the development of a spermatozoid in each of these small cells, the 

 whole of the filling-in tissue falls to pieces, that is to say, the individual cells 

 separate from one another and remain for a short time disconnected but still in 



