296 THE GAMETOPHYTE, AND SEXUAL ORGANS [ch. 



in the prothallial tissue. These characters run parallel with those of the 

 sporangia. The largest sperm-numbers and the most massive and sunken 

 antheridia are found in the Eusporangiate Ferns, where the sporangia also 

 are massive and often deeply sunk, and the spore-output the largest. This 

 parallelism, which however cannot be pursued into strict numerical detail, 

 provides useful material for phyletic comparison. 



The general conclusion which follows from a study of the gametophyte 

 generation in Ferns is that its vegetative characters are deficient in stability 

 and in variety of detail, and consequently they are only of minor importance 

 for phyletic comparison. Of the gametangia the archegonium is so fully 

 standardised that it can only yield material as regards its position relatively 

 to the surface. Consequently it is upon the antheridium that the chief weight 

 of the comparisons must fall. This use of it finds its justification in the 

 parallel which has been traced between the antheridia and the sporangia. 

 The facts and conclusions derived with greater certainty and profusion from 

 the study of the sporangia, as set forth in Chapter Xlll, gain collateral support 

 from those relating to the antheridia, organs quite distinct from them in 

 immediate origin and in function. What thus applies to the antheridia is 

 found to hold also in general terms for the whole gametophyte that bears 

 them. But at best it is only as ancillary to the comparisons based on the 

 sporophyte that the observations on the gametophyte take their natural 

 place in the study of the Filicales. 



BIBLIOGRAPHY FOR CHAPTER XIV 



GENERAL 



230. Engler & Prantl. Natiirl. Pflanzenfam. 1,4, p. 15. 



231. Campbell. Mosses and Ferns. 2nd Edn. 1905. 



232. Campbell. Eusporangiate Ferns. 191 1. 



233. VON GOEBEL. Organographie. li Aufl. Teil ii, 1918, p. 947. 



In these the chief Uterature is referred to. 



SPECIAL MEMOIRS 



234. Bauke. Keimungsgeschichte d. Schizaeaceen. Pringsh. Jahrb. xi, 1876. 



235. Bauke. Aus dem Bot. Nachlass. Bot. Zeit. 1880. 



236. Cramer. Gemmae in Trichomanes. Denkschr. Schw. Nat. Ges. Bd. xxviii, 1880. 



237. Bower. Oophyte in Trichotnanes. Ann. of Bot. i, 1888. 



238. Bower. Gemmae in Trichomanes. Ann. of Bot. viii, 1894, p. 465. 



239. Heim. Unters. iiber FarnprothaUien. Flora. 1896, p. 329. 



240. Jeffrey. Gametophyte in Botrychium vir8,inianu)n. Proc. Canad. Inst. Vol. \- 

 1898. 



241. Britton & Taylor. Life History of Schizaea pusilla. Torrey Bot. Club. 2J 

 Jan. 1 90 1. 



