FEKTILIZATION AND FKUIT-FORMATION IN CRYPTOGAMS. 69 



havo a spatiilato enlargouieut at one oxtremit)'. and carry on the other, attenuated 

 end a regular mane of extremely tine cilia. 



Far more impoi'tant are the cliaracteristics which distinguish from Ferns tlie 

 Rhizoearpefe and Lyoopodialos, especially the genera Salvinia, ilarsilia, and 

 iSdagmdla, in all of which the development has been studied with great care. 

 The antheridia-bearing prothallia are, in the last-mentioned genera, extremely 

 different in point of size from those which bear fruit-rudiments. Both prothallia, 

 it is true, have spores for their starting-points, but these spores themselves have 

 ditl'eront dimensions, and are distinguished as microspon's and viacrosporcs (i.e. 

 small spores and largo spores). The microspores are the parts of the plant where 

 autlieridia are fonned, and the macx'ospores those where fruit-rudiments are formed. 

 In a micivspore the protoplasm divides into several parts, and partition-walls are 

 inserted botwoou them, thus forming a tissue composed of a very few cells, the 

 greater part of which remains concealed in the interior of the spore. Only one or 

 two superficial cells of this tissue push out through rents made here and there in 

 the coat of the spove, and these protruded cells constitute the antheridia. The 

 apical cell of the antheridium becomes tilled with a tissue, and in each cell of this 

 tissue is formed a spimlly-coiled spermatozoid. The opening of the antheridium 

 and the escape of the spermatozoids then ensues in the same manner as in Ferns. 

 The prothallium which originates from a macrospore and is the seat of formation 

 of fruit-rudiments, although it is larger and composed of more cells than that just 

 doseiibed. does not foi-sake the interior of the cavity of the macrospore to any 

 greater extent, but only protrudes a little at one place where the tough outer coat 

 of tl\e macrospore is ruptured. Two kinds of tissue ai-e in reality developed 

 within tlie limits of each macrospore, viz.: the one above referred to as emerging 

 between the toi-n edges of tlie outer spore-coat, and a tissue of reserve material 

 deposited at the bottom of tlie macrospore. The latter is very rich in starch and 

 oil, and serves as a storehouse of nutriment for the prothallium at least until it is 

 in a position to get food for itself out of the environment. The fruit-rudiments 

 (amphigonia) appear on the protruding portion of the prothallium, and are entirely 

 buried in its tissue. The development of the fruit-rudiment, the formation of 

 canal-cells whicli subsequently turn into mucilage, the penetration of the spermato- 

 zoids, and the act of fei-tilization, are in all essential respects the same as the 

 corresponding processes in Ferns, and therefore a desaription of them in detail may 

 here be dispensed with. 



The tissue pi-oduced from a macrospore in the Rhizocarpefe and Selagiuelle:\? has 

 been compxred to the ovule as it occvu'S in the Phanerogams which will be the 

 subject of the next chapter, and certain actual analogies have been brought out 

 which are exhibited by the ooplasm when converted into an embryo, the store- 

 chamber for food-stufls, and the protective envelope in each case. Having regard 

 to the identity of object aimed at through the instrumentality of these structures in 

 the most widely difterent sections of the Vegetable Kingdom, such analogies are 

 reallv a matter of eoui-se, and if naturalists limit themselves to proving that organs 



