ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 597 



sniallness of the leaves was probably compensated for by their multitude. 

 The author finds that there was considerable variety in the respective 

 assimilating systems of the different members of the Carboniferous flora. 



Prothallial Development in Lycopodium.* — H. Bruchrnann gives 

 an account of the germination of the spores and of the development of 

 the prothallium of Lycopodium clavatum, L. annotinum, and L. Selago. 

 Now for the first time there is some information on these matters. The 

 resting-period of the spores is very prolonged; extending to some three 

 to seven years. An unusually small number of spores germinate. The 

 reticulate spores of L. clavatum and L. annotinum belong to an entirely 

 different section of the genus from that which contains the papillate- 

 spored L. Selago : and they produce quite different types of prothallium, 

 which, however, are similar in development. Both the kinds of spores 

 develop independently of fungi, until they consist of five cells, but there- 

 after they are dependent on association with fungi throughout life. The 

 first sign of germination in the spore is the formation of a lenticular 

 cell, which, as in other Pteridophyta, means a rudimentary rhizoid. 



The first stage in the development of the prothallium is an egg- 

 shaped body with two-sided apical cell. In a later stage it differs 

 from all known forms, but is subject to the influence of geotropism. In 

 the second stage of development both forms of prothallium present a 

 radial pear-shaped appearance, and have a meristematic growing-point. 

 The two types now diverge : in the L. clavatum type the prothallium 

 grows slowly, is highly differentiated and capable of resistance ; that of 

 L. Selago is simpler, grows and disappears more quickly. The third and 

 last stage is accompanied by a change from apical to marginal growth, 

 and by the formation of an axial-conducting tissue from a secondary 

 meristem of the middle of the apex. Finally, the middle of the apex 

 is converted into generative tissue and sexual organs, and assumes a 

 dorsiventral mode of growth. In this stage the prothallium exhibits 

 inflorescences and buds. In both types of prothallium the fungus- 

 association inhabits the whole cortical tissue, and is intracellular ; in 

 L. clavatum it is intercellular in the inner layers. The endophytic fungi 

 differ in shape in the two types. In the L. clavatum type the fungus 

 forms balls in the cells, and can pass in and out as it chooses. In the 

 L. Selago type the fungus enters the cells in the form of mycelial threads 

 and sporangioles ; one single infection is enough for the whole lifetime 

 of the prothallium, but the fungus attains a regular communication with 

 the substratum through the rhizoids. The fungus-association in both 

 types brings about a good acquisition of food-stuffs, especially a rich 

 storing of starch. L. complanatum belongs to the L. clavatum type 

 in its prothallium and embryo. L. Selago belongs to the type of L. 

 Phlegmaria. 



Lycopodium Selago : a curious habitat.t — J. W. H. Trail notes 

 the finding of this species on the decaying thatch of an old cottage up 

 the Dee valley. It had produced sporangia and separable buds in plenty. 

 The species has become scarce in the neighbourhood of Aberdeen, owing 

 to the drainage and cultivation of the peaty moors. 



* Flora, n.s., i. (1910) pp. 220-67 (figs.). 



t Ann. Scottish Nat. Hist., No. 75 (1910) pp. 185-6. 



