MEGASPOROI^HYLLS AND OVULES 



347 



needles at their base (Fig. 193, B). The small cones of the 

 Cj'press and Arbor Vita (Fig, 194) occupy a similar position. 



The scale-like sporophylls generally show a spiral arrange- 

 ment, although in Cnpressus and Thuja they are decussate, like 

 the foliage-leaves. In Piniis and other Abietine;e (Larix, Abies, 

 etc.) the axis of the cone bears two different t3'pes of scales 

 which are quite distinct from one another, and occur in super- 

 posed pairs (Fig. 202, D). The lower or bract scale {bs.) of each 

 pair is smaller than the upper or ovulif erous scale (Os.). The latter 

 appears to arise in the axil of the former, and bears, on its upper 

 surface, two ovules (Ov.) whose micropyles face towards the axis 



Fig. 202. — A-B, Structure of male cone of Pinus sylvestris. A, Upper 

 part of cone, in longitudinal section ; B, Single sporophyll. ps., pollen 

 sacs. C, Pollen grain. D, Longitudinal section througli female cone 

 of Pinus. E, Single megasporophyll of Piuiis, from below. F, Part 

 of D, enlarged, bs., bract scale; c, megaspore ; /, integument; 

 m., micropyle ; «., nucellus ; Os., ovuliferous scale ; Ov., ovule. 



of the cone (Fig. 202, E). The difference in size becomes more pro- 

 nounced as the cone grows older, the ovuliferous scale enlarging to 

 a much greater extent than the bract scale. In the Wellingtonia 

 {Sequoia, Fig. 205, D) and Cupressinefe bract and ovuliferous 

 scales are almost completely joined, whilst in some Conifers {e.g. 

 Cryptomeria) the line of fusion is plainly recognisable. The scales 

 in the Cupressineae usually bear more than two ovules, situated 

 with the micropyles directed outwards ; not infrequently the upper- 

 most scales are sterile {e.g. Thuja). The Monkey Puzzles are 

 peculiar in having but a single ovule on each megasporophyll. 



The ovules in all Conifers, apart from those of the Yew-group, 

 possess a single thick integument (Fig. 202, F, I ; Fig. 203, ?'.). This 



