222 Transactions. 



The four protlialli outlined in figs. 52-55 show at their base a distinct 

 fungal tubercle, that in fig. 53 bearing evidence of an original filament. The 

 prothallus in Plate XIV shows a lower fungal region, which was, however, 

 not the first-formed portion. The shaft is long, and bears a lateral process 

 and also a terminal broad generative region which is associated with a 

 second fungal area. In figs. 52 and 54 there is a fungal swelling located 

 behind the growing end, it being evident also that in both tkese prothalli 

 the apex is at the point of renewing its growth. A large number of prothalli 

 of this species which I found were of the peculiar step-like form shown in 

 figs. 52-54. Here the generative regions are sometimes of considerable, 

 extent, and, relatively to the long axis of the prothallus, lie horizontally. 

 The position of these elongated prothalli in the soil is always vertical. The 

 older generative regions are frequently brown and withered, either as the 

 result of a dry spell in the weather or because they have ceased to be 

 supplied with food and have begun to decay. These generative regions 

 are frequently fairly bulky. It is probable that the irregularly, massive 

 forms of prothallus described next have acquired their form through an 

 exceptionally bulky development of one or more of these successive 

 generative regions, the intermediate shaft-like ^stages of growth having 

 been suppressed. Sometimes these massive prothalli show the remains 

 of the lowest shaft and first-formed tubercle still attached to them. 

 Those prothalli of L. laterale which bear club-like processes attached to the 

 primary tubercle, as described in a previous paper (7, fig. 16), probably 

 come under this category. Fig. 55 shows a prothallus which has branched 

 in its middle region, tlie two branches being borne on a particularly large 

 fungal swelling. These two branches are clearly not to be regarded as 

 processes of the kind usually borne on the generative regions. One of 

 them showed a fungal region with rhizoids near its apex. Both are browned 

 at the tip. It is certainly interesting to find that along with its power of 

 cylindrical elongation the prothallus of this species is able also to branch, 

 these variations suggesting that the Lycopodium prothallus is very plastic 

 in character and that the several main types are by no means so fixed as 

 has been supposed. 



'I pass now to the description of the massive and compact prothalli. 

 Some of these show a very regular build (figs. 56, 57, 60, and Plate XV), 

 being comparable with the surfp,ce-growing forms of L. Selago (see 1, pi. 6, 

 fig. 37). They do not, however, show the same internal structure as the 

 latter. The prothallus illustrated in fig. 56 possesses one fungal region only, 

 which occupies the whole of the base. This leads up into a short, massive 

 shaft and a wide, upper, generative region. The whole of the uppermost 

 region is meristematic, there being no localized marginal, ring-like meristem 

 as is the case in the compact prothallus of L. Selago. At the base of this 

 prothallus there is a filament consisting of one long cell bent in the middle 

 (fig. 56a) which does not show the presence of fungus. It leads up into a 

 swollen region which can be described as the basal tubercle, this latter 

 passing gradually again into a higher and more swollen region. The pro- 

 thalli shown in figs. 57 and 60 and Plate XV are also of this same form, there 

 being but one large basal fvmgal region. That in Plate XV is in longitudinal 

 section, but the section does not pass medianly through either the base 

 or the shaft, nor does it show the full width of the prothallus. This 

 massive form of the prothallus of L. ramulosum is similar to that sometimes 

 adopted by the prothallus of L. cernuum and L. laterale, howbeit in a more 

 marked degree. 



